What Causes Bearing Failures and Preventative Measures You Need to Know
Bearings that operate smoothly keep manufacturing processes moving. They are often overlooked parts of the process, despite that they carry the body weight and production load. Bearings often remain invisible until there is a bearing failure in the facility.
So, what is a bearing failure?
A bearing failure occurs when the bearing fails to meet their expected life or performance levels, often causing a machine shaft to fail, and the machine it is apart of can break down.
The consequences of bearing failure are far-reaching for your facility. These can include increased downtime, high-maintenance costs, missed deliveries, loss of revenue and, in some extreme cases, may injure workers.
When a bearing fails, it negatively impacts your facility, your reputation and your bottom line. That said, there are some preventative measures you can take to increase the lifespan of your bearing and prevent improper wear on them.
We know how frustrating it is for a bearing failure at your facility to cause costly downtime and often force you to go outside of your normal supply chain. At Bearing Drive Systems, we’re committed to providing bearing repair services that help you keep your customers through quicker turn-around time.
Whether or not your facility has recently experienced a bearing failure, this guide has everything you need to know regarding bearing failures.
If you’re looking for background on what bearing failure means, different types of failures, common reasons why bearings fail, and actionable tips to prevent bearing failures, you’ll love this guide.
What Is A Bearing Failure How Does It Impact My Facility?
What is a Bearing Failure?
Simply put, a bearing failure occurs whenever a bearing fails to meet its expected lifespan or calculated performance levels.
Bearing failures are more common than you think, and even with careful planning and normal maintenance, they can still fail unexpectedly or prematurely in an application.
L ess than 30% of bearings ever meet their determined fatigue limit and ‘wear out’ in their application [source].
How does the bearing’s fatigue limit and life expectancy factor in to being used for the correct application? It all starts with the original equipment manager (OEM).
According to Flow Control Network, the OEM selects bearings for each application in conjunction with the manufacturer’s designed life expectancy based on a fatigued spall failure.
In general, there are a handful of common reasons why bearings fail:
- Inadequate or improper lubrication
- Contamination
- Improper handling and installation
- Overloading
- . and more!
We’ll discuss these common causes of failure in depth later on in the guide.
The Bearing Failed, Now What?
Bearings are a critical part of any operating machine in a facility, so when you hear an awful noise coming from one of your most important pieces of equipment, you need to act fast.
Bearing failures require immediate attention because they can cause all kinds of headaches in your facility like:
- Unplanned outages
- Increased downtime
- Lost productivity
- Reduced operating efficiency
- Missed deliveries
Not to mention, bearing failures can be costly and can increase operations costs.
However, what’s interesting is that the bearing replacement is often the least expensive part of the failure.
A 50 bearing that fails can cost as much as 25,000-50,000 per hour when it halts production in a multi-million dollar process, according to IBT.
Examining the failure mode, known as the ways, or modes, in which something might fail, will help you determine the exact cause of failure.
But sometimes this examination process ends up becoming complicated quickly thanks to the fact that one failure mode can trigger another.
Here’s an example from Barden Precision Bearings.
Corrosion in a ball race leaves rust-an abrasive-which can cause wear, resulting in loss of preload or an increase in radial clearance. The wear debris can, in a grease-lubricated bearing, impede lubrication, resulting in lubrication failure and subsequent overheating.
If you have a bearing failure in your facility, it is critical to thoroughly assess the situation at hand so you can determine the source of the failure, with the ultimate goal of preventing it from occurring again.
Next, let’s move on to the four stages of bearing failure and how this often shows up on the spectrum.
The Stages of Bearing Failure You Need To Know
As we’ve stated already, bearings do not last forever. They can be damaged and have a shortened lifespan if the right preventative measures aren’t followed through in the facility.
How do you know if a bearing is about to fail?
Almost New Lawn Tractor Runs Then Dies. Step By Step Repair
For starters, bearing failures are sorted into four unique stages.
These stages are based on the types of frequencies produced by the bearing’s rolling elements impacting defects in the inner and outer races.
Let’s dive into the four stages of failure.
Stage 1
In the first stage, you will see small pits begin to appear in the bearing race as well as impacts of rolling elements that show up at ultrasonic frequencies in the spectrum.
It’s important to note that this stage is still considered within the normal operation, so here your bearings are functioning normally.
According to Vibralign, defects appear around 20,000-60,000 Hz and while this isn’t a cause for replacing a bearing, Stage 1 may indicate a lack of lubrication between the races and rolling elements.
Stage 2
Once you reach stage two of failure, you will commonly find that the bearing’s defects begin to ring at its natural frequencies, which ranges from 500 to 2,000 Hz.
Often these frequencies are actually the resonances of the bearing’s components (like the races or rolling elements) or the bearing support structures.
It’s important to note that repairs should be put on the schedule for critical machines at this stage.
Stage 3
At the third stage, the bearing defect frequencies levels become much more apparent and harmonics show up on the spectrum.
You would clearly see defects on the raceways if you were to remove it, and it’s key to determine a deterioration rate at this point.
Furthermore, bearings (in both critical and non-critical machinery) that reach this stage of failure should be replaced, if they’re not already.
Stage 4
Bearings reach this stage when they’re at the end of their lifespan, and you will notice that the noise floor is increased at all levels, which in turn produces a random, broadband spectrum.
Amplitudes of both high-frequency noise floor and HFE may actually decrease, but this is a sign that the bearing is about to fail. [source]
In short, the goal is to prevent bearings from reaching this stage, but if they do, it’s imperative that they’re replaced immediately.
Utilizing these four stages and identifying which stage a bearing is in is critical because not only will it help you foster an accurate predictive maintenance plan, but it will also help you keep your machines operating efficiently and prevent costly, unplanned downtime.
Speaking of failures, let’s move on to discussing in detail the most common reasons why bearings fail that you should keep in mind.
Most Common Reasons Why Bearings Fail
When there is a bearing failure, that means that the bearing motion becomes ineffective. Without proper bearing motion, the machine shaft can ultimately fail, therefore, the machine itself can be damaged and break down.
Regardless if your facility has experienced bearing failure recently, it’s not a surprise to say that bearings are being worn down every minute of active process operation.
There are a handful of causes of bearing failures you can experience, and some are more common than others.
In fact, over 70% of bearing failures are due to poor fitting, poor lubrication, or contamination. [source]
Here’s a chart that better displays the statistics behind common causes of bearing failures.
Let’s dive into further detail about these 13 common reasons why bearings fail as they relate to your manufacturing process.
Improper Lubrication
This should be one of the first reasons considered when inspecting a bearing that has failed. To ensure proper lubrication, adequate viscosity at operating temperature is a must.
Look for highly polished or discolored bearing raceways when troubleshooting to determine if working surfaces are lacking adequate viscosity at operating temperature.
Over-lubricating can be just as detrimental as under-lubricating.
Under-lubrication risks metal-to-metal contact, over-lubrication causes heat build-up and friction as the rolling elements continuously try to push extra grease out of the way. according to IBT.
Cage Damage
There are numerous causes for cage damage. Some of the more common ones include vibration, excessive speed, wear, or blockage.
Contamination Corrosion
There are many contaminants that can cause problems with a bearing. Dirt, sand, and water are the most common ones that you run into, but chemicals and corrosives can also damage bearings.
These contaminants reduce viscosity which causes corrosion to the bearing surfaces, disrupts the oil film, and causes erosion, leading to the creation of countless abrasive particles.
Be sure to keep work areas, tools, fixtures, and hands clean, as this prevents and contamination failures. [source]
Electric Arcing
Also known as Electric Arc Erosion, this failure occurs when an electric current passes through the bearing and is broken at the contact surface between races and rolling elements, producing high temperatures at localized points. [source]
This can damage the bearing by creating pits on the raceways and rolling elements.
Poor Fitting
It’s vital that the bearing is properly mounted to an accurately sized shaft. If it isn’t, it can cause issues in two ways:
If the shaft is oversized or expands, it will result in too tight of a fit, reducing the bearing’s internal clearance (see more on this below).
If the shaft is undersized or has too loose of a fit, the bearing will creep on the shaft and will wear and create heat, which eventually will result in vibration and runout problems.
Fatigue
Often referred to as spalling, fatigue failure occurs when there’s a fracture of the running surfaces, which leads to the removal of tiny, detached particles of bearing material.
Since this type of fatigue is progressive, once it begins, it will continue to spread as the bearing operates. A key indicator of fatigue to keep an eye on is an increase in vibration.
While fatigue may occur at the end of the bearing’s normal life expectancy, it frequently occurs before then due to an excessive loads, according to AST Bearings.
Brinelling
This type of failure occurs when loads exceed the elastic limit of the ring material and can be identified as permanent indentation marks in the raceways, which cause increased vibration.
-
True brinelling. caused by exposure to loads that exceed the elastic limits of the bearing material.
Check out this video below from The Audiopedia to learn more about brinelling.
Misalignment
Misalignments lead to excessive vibration and loads. Some bearings (not all, though) can handle minor misalignments.
According to Bearing Failure: Causes and Cures, the most commonly found causes of misalignment include: bent shafts, dirt or burrs on shaft or housing shoulders, shaft threads that are not square with shaft seats, and locking nuts with faces that are not square to the thread axis.
To prevent misalignment, there are a few best practices you can keep in mind.
Ensure you inspect shafts and housing regularly, use precision-grade locknuts, and shim the housings as needed.
Path Patterns
To gain a better idea of the conditions a bearing was operated, it is best to examine the wear path pattern of the dismantled bearing that’s already been in service.
Through failure analysis testing and the understanding of normal/ abnormal wear path, one can correctly assess if the bearing has been run under the ideal conditions.
Seal Selection Maintenance
Adequately sealed bearings guard against contamination and ensuring the lubrication isn’t destroyed.
Here are some guidelines for selecting and maintaining seals from Flow Control Network:
- Utilize seals that can withstand the chosen environmental/operating conditions of the facility.
- Install external shields to prevent the build-up of debris on and around seals, when possible.
- Be sure to schedule routine checkups on the radial lip seals for flexibility, hardening, cracking, and shaft contact.
- Inspect for leaks and replace damaged seals quickly.
- Steer clear of purging excessive grease past the lip seals. This can cause them to lose contact and their effectiveness and in some grave cases, can be dislodged from the housing.
- Proceed with caution if you’re using water, steam, or compressed-air sprays when cleaning. It’s easy to accidentally damage seals and force contaminants into otherwise clean equipment.
- If you’re taking large machinery apart, avoid lifting with chains, wire ropes, or dirty slings that can score sealing surfaces. If the seal contact surfaces are worn down, be sure to resurface and grind them to meet their original specifications for finish and diameter.
Overload
Putting too much load on a bearing is a common cause of failure.
You can troubleshoot overloading by reducing the load on the bearing or considering using a bearing with a greater capacity.
Improper Handling Storage
Simply put, improperly storing bearing causes issues later on because they’re exposed to outside elements like dampness, dust, and varying temperatures.
Handling becomes an issue when boxes are opened, or wrappings are torn prematurely because it can expose the bearings to dirt and corrosive elements.
Reliable Plant says to be sure to watch out for dampness and temperatures that could cause rust or uncovered bearings in the storage area.
Inadequate Internal Clearance
Last but not least, this failure impacts friction, load zone size, and fatigue life of a bearing. If the clearance of the bearing is inadequate, excessive heat will build up.
As we’ve discussed already, high temperatures do not fare well for bearings and can cause other problems already listed as in lubrication and internal friction.
Now that you know more about the most common types of bearing failures you can witness in your facility, how exactly can you prevent a bearing failure?
Keep on reading to find out about our top preventative measures that you can implement at your facility today!
Preventative Measures for Bearing Failures To Keep in Mind
Under normal operating conditions, bearings have a substantial service life, but since they do have a fixed lifespan, it’s inevitable that a bearing will eventually fail.
Actually, less than 1 percent ( 0.35 percent specifically) of rolling bearings do not reach their expected life. [source]
The key to preventing downtime and lost productivity in your facility is to prevent premature failure, which stems from damage that occurs to the bearing that usually could have been halted.
Doing so can not only help you prevent premature failure, but it can also help keep your process moving smoothly as well.
The majority of bearing failures we’ve discussed above (think pitting, spalling, unusual wear patterns, rust, corrosion, etc.) trace back to a small group of causes that are not only interrelated but are fixable too.
These causes are mounting/ alignment, lubrication, operational stress, environmental influence, and improper storing.
Why Proper Mounting and Alignment of Bearings Matters
It’s imperative that the proper tools, ovens, and induction heaters are used during the mounting and installation process of bearings.
Be considerate of avoiding misalignment or shaft deflection, as this is significant in mounting bearings with separate parts. Without proper alignment between components, the bearings will end up experiencing abnormal wear.
Once you’ve completed installation based on manufacturer’s instructions, a best practice to keep in mind is giving the bearing a solid flushing and cleaning out with lubricant. Additionally, be sure to apply the final proper amount of lubrication before the machine is used.
This leads us to the next preventable measure. lubrication!
Lubricate According to Manufacturers’ Guidelines
Lubrication is used on bearings to cover the rolling completely and sliding surfaces with a thin oil film to prevent metal-to-metal contact.
Grease is more commonly used because it’s easy to handle, while oil lubrication is frequently used with high-temperature or high-speed applications.
Common lubrication failures occur due to:
- Using the incorrect type of lubricant
- Too little grease/oil or too much grease/oil
- Mixing grease/oil
- Contaminating the grease/oil by objects or water
According to Machinery Lubrication, when applied correctly and effectively, lubrication helps reduce issues like friction and abrasion, transports heat generated by friction, prolonging service life, prevents rust and corrosion, and keeps foreign objects and contamination away from rolling elements.
Prevent Operational Stress
Operational stress on a bearing can impact bearing life.
- If the load is too low on a bearing, it will result in skidding and improper loading of the rolling elements.
- If the load is too high, it could result in overloading and early fatigue.
Normally, the first sign of issues like these is unusual noises and/or elevated temperatures. The desirable bearing temperature is somewhere below 100 degrees Celsius.
It’s important to note that bearing temperatures usually increase with start-up and level off at a temperature slightly lower than the start-up (ranging from 10 to 40 degrees Celsius higher than room temperature).
That is why it’s crucial to make sure vibrations are isolated in associated equipment because if they’re not isolated, they can cause unusual noises and uneven running.
Take Environmental Influence Into Consideration
If not taken into consideration, there are numerous operating environments that can bring down even the best bearing and cause a failure. Here is a list of the primary issues you should have on your radar.
Dust and dirt, which can contaminate a bearing at an aggressive rate. Be sure to use proper sealing techniques to prevent this type of contamination.
Aggressive media or water. This is another instance where proper sealing is crucial.
External heat. Ambient operating temperature mandates many choices in radial internal clearance, high-temperature lubricants, intermittent or continuous running and other factors that affect bearing life. [source]
Current passage or electrolytic corrosion. Sparks can create pitting or fluting on bearing surfaces if current is allowed to flow through the bearing’s rolling elements. You can fix this by using insulation on or within the bearing or creating a bypass circuit for the current.
Store Your Bearings Actively
Present-day, a majority of facilities keep the number of spares they have in stores a minimum.
Thanks to preventative maintenance (like the other measures we’ve mentioned above), facilities can detect potential failures earlier.
This means facilities can order and replace the damaged bearings before an entire machine breaks down, making the need for spare bearings to sit on shelves practically obsolete.
When you need to have bearings being stored in your facility and sitting on shelves, be sure to store them actively. This can be accomplished by rotating or spinning them frequently.
If bearings don’t receive occasional rotations, it can cause false brinelling to occur, which is a premature failure we discussed in Chapter 3.
Conclusion
Bearings are typically very reliable, even under the most rigorous conditions, and under normal running conditions, a bearing’s service life is substantial.
When a bearing does fail prematurely, it’s often due to causes that can be avoided. For this reason, it’s crucial to be able to identify the root causes to prevent future failures with preventative measures and the issues that follow them.
Accurately diagnosing and troubleshooting bearing failures in order to get ahead of them will help prevent repeat failures and additional pain-points your facility might be experiencing, such as decreased operating efficiency, increased downtime and lost revenue.
As a premier source of bearings and power transmission products to the global distribution market, Bearing Drive Systems is committed to delivering a quality, authentic product to meet our customer’s expectations.
If you’re looking for a solution that very few vendors provide that offers a significant cost saving, our bearing repair services could be a great way to get your foot in the door or build your existing relationship with your customers.
Lawn Mower Runs For Thirty Minutes Then Dies (This is why)
What a pain in the jacksie! Halfway through the yard work, she stalls. But don’t panic, you are in the correct place, and very soon, you’ll know what the problem is and how to nail the repair.
The most common cause of a mower that runs for thirty minutes and then dies is a faulty armature. A faulty gas cap is the second most likely cause.
In this post, you’ll learn the most likely cause of a mower engine stall after thirty minutes, and you’ll learn how to test and fix it.
Mower Gas Cap
A faulty gas cap is, as you know, the second most common cause of a mower stalling after thirty minutes. I’m covering it first because the gas cap is really easy and fast to check. All mower gas caps are vented, which basically means the mower gas tank must allow air to enter the tank to replace the fuel that leaves. If the tank is sealed, the fuel becomes air locked, and the mower stalls.
This typically happens after a short period between ten and thirty minutes and also depends on factors like weather and gas tank fuel level.
Need more info on the fuel system, carburetor components, and how they work, you can check them out here.
Faulty Cap
Commonly gas caps are lost, and the owner may MacGyver up an oil can cap that fits like a glove. While on the face of it, this seems like a coincidence. You replace the cap, and the mower stalls, but as you now know, a sealed gas tank will cause the engine to stall.
Anyway, if you’ve got a makeshift gas cap fitted, it’s likely your problem. But even if you haven’t, gas cap vents do fail, but we’ll eliminate it as a possible with this simple, fast test.
Work the mower in the usual way until it stalls, then go ahead and follow these steps:
MacGyver didn’t get it right every time.
If the mower starts and runs as normal, then your gas cap is faulty, go ahead and replace it. If, on the other hand, the mower still won’t start, you’ll need to check the mower for spark. Checking spark isn’t difficult, and it’s all covered below.
What Is Mower Armature?
A mower armature is a small component fastened to the exterior of the engine; some may refer to it as a coil. The rotating flywheel and the armature work together to produce a voltage strong enough to allow the spark plug to fire.
Armatures commonly fail in two ways, they stop working, and your mower won’t start, or they work when the engine is cold but fail as the engine heat soaks into the windings of the armature. Armatures are solid-state components. They aren’t repaired. They are replaced.
Check out the Amazon link below for common lawnmower armatures.
Armature – Common cause of hard hot starting and running issues.
Where Is My Mower Armature Located?
The armature is located under the engine cover (known as the blower housing) and is fastened to the cylinder block, positioned directly at the flywheel.
Location – Armature and flywheel
Test A Mower Armature
To test the armature, you’ll need a helper to simulate starting the mower while you check the spark. You’ll also need insulated pliers and a plug wrench. The process is simple, but you’ll need to use caution. Keep hands and feet clear of the mower blade as the engine is cranked over.
As we are chasing an intermittent failure (fails when the mower is hot), checking the spark when the engine is cold won’t be useful (we expect it will work great then). We’ll need to cut some grass until the engine warms up and stalls.
That’s when we’ll check for spark. Now, we’ll need all our tools to hand; allowing the engine cool will, as you know, mean the fault disappears again. Let’s get testing so.
Testing Spark
Using a spark test tool is preferred, but I’ll cover the whole process here in this post – MacGyver style.
You may find these videos useful also:
Need info on how small engine ignition system works, check this out.
The spark testing process is as follows:
Remove – Remove the spark plug wire (twist and pull) and also the spark plug.
Fit – Refit plug wire
Ground – Ground the plug wire on any bare metal, but you’ll need to use insulated pliers to hold it in place while the helper pulls on the starter cord.
Attempt Start – Si mulate engine start (Helper pulls on the cord) while you view the spark plug.
Repeat – Try another spark plug to eliminate a faulty plug; failing to test with a second plug means you could condemn the armature in error.
Result
No spark means the armature has failed; go ahead and order a replacement. Armatures all look alike, but there are a ton of different types. Remove the old armature, check the part number, and order its replacement by part number, not by mower model.
If you have spark, your armature is good, and it’s likely you have an over-fueling carburetor issue (see below), usually caused by a faulty auto choke system. A replacement carburetor will likely fix the issue but first, check for binding auto choke controls. I’ve covered choke testing and carburetor replacement on this page; it contains several videos – “Choke testing”.
Replacing Mower Armature
To remove the armature, you’ll need a screwdriver, ratchet, and socket set, and you’ll need to remove the following:
- Engine cover (Blower housing)
- Armature fasteners
- Plug wire
- The stop-start armature control wire
Fitting Armature
Replacing the armature is the reverse. However, when fitting the armature, an air gap between the armature and the flywheel must be maintained in order to generate a sufficient spark. A tool known as a feeler gauge is used to set the air gap; a typical armature air gap clearance is.010 –.014in.
Most won’t have a feeler gauge, and that’s OK; you can use a business card to set the gap. If you need more detailed instructions with pictures, check out this post, “Mower hard to start when hot” it covers the replacement procedure in full with pics.
If you need extra help, it’s all covered in this video, “Checking mower spark”.
Mower Stalling After Grass Bag Emptying
Some mowers equipped with the auto choke function may have difficulty starting when hot. Typically an operator stops the mower to empty the grass box, and the mower won’t restart. Wait ten minutes or so, and the mower starts.
The root cause is a defective auto choke, causing the engine to flood with too much gas.
Check the auto choke system is working without fault; it’s all covered on this page under “Choke testing”.
Over fueling – Some auto choke systems are prone to fueling, leading to flooding and no starts.
Riding lawn mower engine won’t turn over or click video
If your riding lawn mower doesn’t do anything when you turn the key to start the engine, it could be a variety of things. This video shows you how to pinpoint the cause by checking the riding mower’s battery, solenoid posts and coil, fuse, ignition switch, brake switch and blade switch. It also walks you through how the starting system works, so you can better understand how to track down the problem.
For additional repair help, including common symptoms and troubleshooting tips, step-by-step riding mower and tractor repair guides and articles, check out our repair help section. In addition, find the riding mower parts you need to fix your mower.
Riding Lawn Mower Shuts off After a Few Minutes
Hi, this is Wayne with Sears PartsDirect. Today we’re going to troubleshooting a riding lawn mower that doesn’t do anything when you turn the key to start the engine—not even click.
Before you do anything, make sure the parking brake is set and the blades are disengaged. The riding mower won’t start otherwise. You’d be surprised how many people forget those steps and think something is wrong with their riding mower.
Supplies you might need
- Work gloves and safety goggles
- Multimeter
- Wire brush
- Clip-on meter probes
- Wrench set
What went wrong
What is the significance of the click when you turn the key? When you hear the click, you know the starter solenoid coil is getting power from the battery through the ignition switch.
If you don’t hear that click, either the starter solenoid has failed or the starter solenoid coil isn’t getting power.
We’ll show you how to pinpoint the cause by checking the riding mower’s battery, solenoid posts and coil, fuse, ignition switch, brake interlock switch and blade switch.
We’ll use this Craftsman riding lawn mower for our troubleshooting. This type of riding mower is common, but the wiring and components in yours might be different. Refer to the wiring diagram for your model if you notice differences.
How the riding mower starting system works
To understand how we track down the problem, it helps to know how the starting system works:
- The positive, red battery cable connects to one of the two large terminal posts on the starter solenoid.
- The black wire connected to the other large terminal on the starter solenoid carries power to the starter motor to start the engine.
- A small red wire branches off the red solenoid terminal post to carry power through the ignition switch to the coil at the bottom of the starter solenoid.
- When you turn the key to the start position, the ignition switch sends power through the white wire and energizes the coil inside the solenoid. The coil closes an internal contact to send power from the red battery cable to the black wire, which powers the starter motor to spin the engine.
Is the battery dead?
So what can go wrong with the starting system?
Well, a dead battery won’t power up the starter system and could prevent the solenoid coil from clicking.
To check the battery, we’ll use a multimeter to measure the DC voltage across the battery terminals.
- Put on work gloves and safety goggles.
- Turn off the ignition.
- Access the battery. In this type of riding lawn mower, you lift the seat to get to the battery.
- With the multimeter set to measure DC voltage, touch the red multimeter probe to the positive or red battery terminal and the black meter probe to the negative or black battery terminal.
- If the battery is good, it measures more than 12 volts DC.
- If it measures less than 12 volts, the battery is weak or dead and you’ve likely found the problem. A weak or dead battery won’t power the starter solenoid coil.
Try recharging the battery using a charger. Or, in a pinch, you can use jumper cables to jump-start a riding lawn mower model that uses a 12-volt battery.
If the battery won’t recharge, replace it.
Check for power to the solenoid
If the battery is okay, it means power is getting to the red battery cable. But, is voltage getting through the red battery cable to the red terminal post? To check that, let’s measure voltage at the red terminal post.
With the multimeter set to measure DC voltage, touch the red meter probe to the red post on the starter solenoid and the black meter probe to the negative terminal on the battery. It should measure more than 12 volts.
A word of warning here: Don’t let the meter lead touch both the solenoid posts at the same time or you’ll see a severe spark. Shorting across the solenoid posts sends the current to the starter motor. Some of you may be tempted to short across the solenoid posts intentionally using an insulated screwdriver to start the engine. But we strongly discourage this approach, because this dangerous practice overrides safety switches.
If the meter measures less than 12 volts, check the battery terminals and cable leads for corrosion. Clean corrosion off the battery terminals and battery cable leads with a wire brush—corrosion can prevent the red solenoid post from getting power. Recheck the voltage. If it still doesn’t measure more than 12 volts at the red post, replace the red battery cable.
Check for power to the solenoid coil
So, let’s get back to troubleshooting the starting system.
Now that we know the red terminal is getting power, the next step is to find out whether the solenoid coil gets power when you turn the key.
If you measure voltage at the coil but the internal contact doesn’t click, the starter solenoid is to blame. The solenoid clicks when it sends power to the starter motor.
To check voltage on the solenoid coil wires, you need clip-on meter probes to hold the probes on the wires as you turn the ignition key, unless you have a helper to turn the key while you hold the probes on the wires.
- Pull the white and black wires off the spades of the solenoid.
- Set the multimeter to measure DC voltage.
- Clip the red meter probe to the white wire female spade connector and the black meter probe to the black wire female spade connector.
- Turn the ignition key to the start position, note the voltage reading on the meter display and then turn the ignition key off.
- If the multimeter measures battery voltage, it will be more than 12 volts. Replace the starter solenoid because the coil is getting power but not closing the internal contact to send power to the starter motor. Here’s a video that shows you how to replace the starter solenoid.
- If it measures 0 volts, there’s a break in the circuit to the solenoid coil. The starter solenoid is likely okay, it’s just not getting power. Time to test the coil circuit.
Test the coil circuit
We’ll check the ground side of the circuit first. The black wire attaches to the solenoid coil and connects to the metal frame of the riding mower as a ground. A break in that wire keeps the coil from getting power.
To check the ground wire, we check for resistance between the female spade on the black wire and the metal frame of the mower.
- Disconnect the negative battery cable and then the positive battery cable to completely kill power to the mower before checking resistance.
- Tuck the cables away from the battery to keep them from touching the posts and accidentally restoring power.
- Set the multimeter to measure resistance and touch one meter probe to the black wire female spade and the other meter probe to bare metal on the mower frame to ground it—I’m using the mower deck height lever.
- A reading near 0 ohms of resistance means the black wire is grounded.
- A reading of infinite resistance means you must to find and repair the break in the black ground wiring. Once you restore a good path to ground on the black wire, you should be able to start the engine.
Check the fuse
If the ground side of the circuit is okay, we’ll check the hot side of the circuit that begins with the small red wire on the starter solenoid terminal and ends at the white wire that connects to the coil spade.
The circuit includes a fuse, the ignition switch, brake switch and blade switch.
First, we’ll check for a blown fuse because you can usually see a blown fuse just by looking at it.
The fuse in this mower is right here next to the starter solenoid, but we need to pull out the battery and battery box to access the fuse.
Move the zip tie over and pull the fuse from the holder.
If you find the fuse element broken like this, replace the fuse because it’s definitely blown.
If you’re unsure whether the fuse is blown, check for continuity through the fuse using your multimeter. Place one meter probe on each of the fuse leads to measure resistance through the fuse. You should measure near 0 ohms of resistance through the fuse. If you measure infinite resistance, replace the fuse because it’s blown.
Keep in mind that the fuse blew because of a short in a component or wiring. Follow the steps in this video to determine the cause of a blown fuse and fix the problem so the fuse doesn’t blow again soon after you replace it.
If the fuse is okay, reinstall it in the holder and secure it with the zip tie.
Test the ignition switch
Next, we’ll check continuity through the red wire from the starter solenoid post to the ignition switch.
- Open the mower hood.
- Pull the wire harness off the ignition switch.
- Release the locking tabs on the ignition switch and push it out of the dash.
- Push the wire harness plug through the hole so you can easily access the contacts for testing.
- With the multimeter set to measure resistance, place one meter probe on the starter solenoid post with the red wire and the other meter probe on the female plug spade with the red wire attached.
You should measure near 0 ohms of resistance through this section of wiring. If you measure infinite resistance, find and repair the break in the red wire.
If this section of wiring is okay, we’ll test the ignition switch next.
When you turn the key to start the engine, internal ignition switch contacts should complete a circuit from the red wire on the B terminal to the white wire on the S terminal.
To test the ignition switch, we’ll measure the resistance between terminals B and S with the key turned to the start position. With the multimeter set to measure resistance, touch one meter probe to the B prong on the back of the ignition switch and the other meter probe to the S prong. Turn the key to start the engine and check the resistance in your meter display.
You should measure near 0 ohms of resistance. If you measure infinite resistance, then replace the ignition switch because it isn’t closing the contact B to S to send voltage to the solenoid coil.
Test the brake interlock switch
If the ignition switch is okay, then we’ve isolated the circuit break to the section of white wire that includes the brake switch and blade switch.
We’ll check the brake switch first. To give you a better view, we’ve removed the hood.
- To access the brake switch, remove the air duct mounting screws and pull off the air duct.
- Carefully move the fuel tank out of the way. Drain some fuel from the tank if it’s too heavy to lift.
- Next, remove the lower right dash fastener and pull off the lower dash. Now you can get to the brake switch for testing.
- Note the prongs that the white wires connect to because those are the prongs that we’ll check resistance through to determine whether the brake switch is okay.
- Pull the wire harness off the brake switch.
- With your multimeter set to check resistance, touch one meter probe to one prong and the other meter probe to the other prong that connects to the white wires.
You should measure near 0 ohms of resistance if the brake switch is okay.
If you measure infinite resistance, replace the brake switch because it’s broken. Here’s a video that shows how.
Check the blade switch
If the brake switch is okay, we’ll check the blade switch.
- Remove the clutch lever assembly mounting screws and pull the assembly down slightly to access the blade switch.
- Note the prongs that the white wires connect to and then disconnect the wire harness from the blade switch.
- With your multimeter set to check resistance, touch the meter probes to the prongs that the white wire connected to.
The multimeter should show near 0 ohms of resistance if the blade switch is okay. If it measures infinite resistance, replace the blade switch because it’s broken.
If the blade switch is okay, then there’s a break in the white wire between the ignition switch and the solenoid coil that’s preventing the coil from getting power. Find and repair the wiring break.
Now that you’ve gotten through all of our troubleshooting tips, you should be able to start your mower. Now you can get to the real work of mowing your lawn!
I hope this video helps you out today. Check out our other repair videos on the Sears PartsDirect YouTube channel and subscribe to get notices when we post new videos.