The Power Take-Off (PTO) clutch is a part that disconnects transferred power from the engine to another piece of equipment on your lawn tractor such as the transmission. It’s a part that’s put under tremendous pressure, and there is a range of problems you may experience when a PTO clutch goes bad.
Some of the most frequent signs of a PTO clutch failing are grinding noise when engaging the blades, jerking or shuddering when blades are in use, difficulty engaging the blades, or reduced power. Unfortunately, when this happens, the best course of action is to replace the PTO clutch. Fortunately, it’s not that difficult to replace.
Keep on reading as we go over troubleshooting a bad PTO clutch, what the signs and symptoms are, and how to replace one on your lawn mower. Get your tools ready, pull up a seat, and let’s dive in.
How Do I Test A PTO Clutch?
Testing your PTO clutch is essential in ruling out other possible issues in your riding lawn mower. To do this you’ll need some jack stands or vehicle ramps, something to chock the mower’s tires, and a multimeter.
Secure the mower by setting it on the jack stands, though vehicle ramps are more stable. Next, chock the rear tires so they won’t roll off the stands or the ramp. Now, perform a visual check of the mower deck, belts, and blades.
If there are any grass clumps, or other debris along the belts, pulleys, or around the blades, be sure to clean all that up and remove it. Now, put the mower back on the ground and start the engine, then engage the blades a few times.
If you hear any abnormal noises or grinding, or if the blades start then stop on their own, or if they aren’t running at the proper speed, you probably have a bad PTO clutch. If they don’t engage at all, you can check a few other parts.
First, use the multimeter and check your lawn mower battery. If it is weak, it may not have enough power to engage the PTO clutch. Charge your battery, or replace it and see if that fixes your issue. You’re looking for at least 12.4 volts or higher. Anything less may not be enough to engage the blades.
After checking your battery, either use the multimeter or visually inspect the fuses. Any brown, black, or blown fuses need to be replaced. Any fuses that don’t give you a reading on your multimeter need to be replaced.
That’s how you check your PTO clutch, but what are other symptoms that your PTO clutch is bad, or it has failed completely? Let’s look at those symptoms now.
What Are The Symptoms of a Bad PTO Clutch? (How To Fix It!)
There are many different symptoms of a bad PTO clutch, and not all of them are related to the blades turning or not. It can be confusing trying to troubleshoot a problem when it comes to lawnmowers. Here we try to remove any confusion so you know exactly what to be on the lookout for.
Symptom #1. Hard To Start
When it takes time for the blades to run at the proper RPMs that’s a common symptom of a bad PTO clutch. The clutch hasn’t completely failed yet, but it’s definitely on its way out.
This will also generate a lot of heat because friction prevents the blades and pulleys from turning at normal speeds. If the PTO clutch heats up enough you may notice smoking, a foul, burning smell, or may even start a fire.
Especially if there are a lot of grass cuttings around the heat source. So, if you notice the blades are having a hard time starting up, quit using the mower until you get it repaired.
Symptom #2. No Sound When Engaging PTO
When you switch on the mower blades but you hear no sound whatsoever, you may have a bad solenoid. We have already checked the battery, and the fuses so those parts should be working fine. Now we need to check the solenoid.
The PTO solenoid is an electromagnetic switch that activates the clutch. Not all mowers will have this feature as this is usually located on mowers with electric PTO switches, not manual levers.
To test the PTO switch, we need the trusty multimeter again. With the mower switched off, unplug the wire that comes from the PTO switch. Now turn the mower key to just one click. You’re not starting the mower, just activating the battery.
Switch your multimeter to test Amps. Place the black probe on grounded metal, and insert the red probe into the PTO switch wiring harness. When you press the PTO button, you should see a reading on your multimeter of about 4 amps.
No reading means you have a bad switch.
If the switch is functioning, then you need to check the solenoid itself. Switch the multimeter to Ohms and test the solenoid. You should see a reading between 4.7 and 5.9. Anything outside of that range means it’s bad and needs to be replaced.
Symptom #3. Mower Blades Stop Dead
A pretty good sign that your PTO clutch has failed is your mower blades stop completely for no apparent reason. If you’re mowing, you haven’t hit anything like a branch, rock, or stump and the blades stop on you for no apparent reason, the PTO clutch just went out on you.
It could also be a sign that you have just blown a fuse, so check your fuses when you are able to get stopped and turn the engine off.
Symptom #4. Clutch Won’t Engage
Typically your PTO clutch won’t one day, then absolutely refuse to work the next day without noticing something “off.” Now, it could be that the blades were working ever so slightly slower that you didn’t notice it, and then it seized up while the mower cooled off.
But usually, you will hear some sort of grinding noise when you start the mower blades, you may hear a slight or very loud squealing noise, or you may notice that the blades don’t spin as fast as they used to.
It could be that the bearings were starting to go out, and this last time, they finally seized up when you were finished mowing. Now they won’t engage at all. You try to engage and disengage the blades but nothing happens, this means the PTO clutch is finished.
Symptom #5. Noise Coming From the Mower Deck
Noises coming from the mowing deck when the blades engage could be either a belt problem or the PTO clutch. Of course, you’re going to hear the sound of the blades spinning when they start, but any abnormal noise needs to be inspected.
Just be sure to NEVER get near the blades while they are engaged and spinning. Before investigating any strange noise from the mower deck, turn off the mower, and remove the key just to be safe.
Now that everything is turned off, visually and physically inspect the mower belts. They should be snug and in place. There should not be any physical anomalies like pits, cracks, frays, or chips. If there are, replace the belts before using the mower again.
Now inspect the pulleys. Make sure they are not loose, bent, or damaged. All of these issues could create abnormal noises.
Squealing and grinding noises could signify a bad bearing or a bad PTO clutch. Later we will tell you how to replace it.
Symptom #6. PTO Switch Not Responsive
For those mowers that have a PTO switch instead of a lever, you could have a bad switch, a blown fuse, or a weak battery if you press the switch and nothing happens. You may even experience an engine stall when you press the switch.
When this happens check your battery first. You need to see at least 12.4 or 12.6 volts on your multimeter for it to activate the mower blades. If you don’t see these voltages or higher you’ll need to charge your battery until it has enough charge.
A weak battery could mean your battery is going bad, you have corrosion on the terminals, the battery needs to be serviced, or you have a weak or dead alternator on your mower.
Next check any inline fuses, and the fuses in your fuse panel. You can take them out and look at them one by one, or use the multimeter to check them. Fuses have a thin metal filament that connects both sides.
If there is any discoloration or the metal is no longer connected, you need to replace the fuse. Fuses are very inexpensive, but if you constantly have to replace them, you may have a short somewhere that needs to be repaired.
Don’t be tempted to put a higher amp fuse in its place to keep it from burning out. Always replace fuses with the same amperage. Putting a higher rated fuse in nullifies the safety feature and could lead to more extensive electrical damage, or a fire.
After checking all those places and you still can’t get your PTO to engage, you probably have a bad switch. If that’s the case, contact the manufacturer to order a new PTO switch or take the mower to the mechanic and have them put one in for you.
How to Solve Bad PTO Clutch Symptoms
By following the steps outlined above you can check to see if the PTO clutch is going bad, if it’s the solenoid instead, a failing PTO clutch switch, or something non-related.
When the battery isn’t strong enough to engage the mower blades you’ll have to service the battery or replace it.
Fuses are easy to replace, but if you replace the same one often, you’ll have to figure out what is causing it to burn out so quickly. Most likely you have a short caused by a damaged wire somewhere.
Lastly, if there is nothing else causing the bad PTO clutch symptoms, you need to replace the clutch itself. This isn’t usually a difficult job, but if it has fused or become rusted then it can become difficult or downright impossible without a tool called a puller.
How Do You Remove A PTO Clutch?
You’ll need vehicle ramps or jack stands, a pry bar or flat screwdriver, and a few socket wrenches to replace the PTO clutch.
Locate where the PTO clutch is situated on your mower. It’s usually in the back but could be elsewhere on some brands. Then carefully mount the mower on the jack stands or ramps and make sure it’s secured and won’t fall or roll off.
Next, disconnect the plug wire from the spark plugs just to prevent it from starting. Now disconnect any guards or coverings protecting the PTO clutch, then loosen the belt.
You should see a set or two of wires that connect directly to the PTO clutch. Carefully disconnect these, then remove the center bolt. Now is when it can be difficult to get the clutch out.
You may need the pry bar or flathead screwdriver to carefully pull the PTO clutch off the spindle. If it’s really stuck you may need to purchase or rent a hub puller that will help you get the clutch off.
You don’t want to shake or hit the mower while it’s suspended as it could fall, so be very careful during this step. At any time, if you feel you are over your head, or this is beyond your mechanical know-how, don’t be ashamed to take the mower to a mechanic. There’s nothing wrong with having a professional do this for you.
The main symptoms of a bad PTO clutch include abnormal noises, problems engaging the mower blades, they stop working with no warning, or the PTO switch is unresponsive. When this happens you can test the clutch, and the battery to see if either one is going bad.
When you find out the culprit, you can fix the problem. Unfortunately, when the PTO clutch starts failing, all you can do is replace it. While that job may not be too difficult, sometimes it can be too hard for everyday people like you and me to handle. In this case, it’s best to consult a mechanic.
Ruben has been doing online marketing for the last 4 years. Prior to that, he spent 15 years managing different brick-and-mortar businesses, in the home improvement and logistics industries. Overall, he has 20 years of business experience under his belt. Recently, he added SEO, affiliate marketing, and link building to his business skills.