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How Do I Know if My PTO Clutch Is Bad?

A PTO clutch is a clutch that is commonly found on lawn mowers. A PTO clutch is a device that is used in a lawn mower to engage the blade. It’s responsible for engaging the blade and is connected to the engine power. 

It is responsible for engaging the blade when the engine power has been transferred to the drive train. The device controls the mechanical disconnect between the power created by gas and diesel engines. 

It enables the transmission of that energy to auxiliary devices like hydraulics, alternators, electric-only motors, etc. A PTO clutch is important for keeping your lawn mower running smoothly.

If you don’t have a PTO clutch in your mower, then every time you start it you will notice a winding problem and failure in pulley bearing or it could even break down from overloading which is rear. 

There are a number of symptoms that can indicate a bad PTO clutch. In this article we’ll discuss the symptoms of a bad PTO clutch and how to fix the issues.

PTO Clutch of a lawn mower
PTO Clutch of a lawn mower

PTO clutch failure modes

The clutch failure modes are grouped based on the different ways they may cause the machine to shut down. It is important that you know what causes your mower to stop working and how to fix it.

There are two common failure modes in the lawn mower: winding and pulley bearing. It is possible for mechanical damage to happen. 

It is very important to know how and why your mower stopped working so that you can avoid future problems with it.

Bad PTO clutch of a lawn mower
Bad PTO clutch

Windings failure

When wires are used, they warm up. Wires get hot and contract when they’re removed from the PTO. The movement seems to scrape the thin, varnish-type insulation from all of the wires in the wiring system. 

This creates a short that can lead to a fire or worse. An electromagnet strength is defined by its number of coils and the current running through its wires. 

With wires that are shorting out, the wire resistance reduces and there is more current going through. This normally overpowers the other circuits in the system, causing your electrical system to trip. 

Placing a resistor in your windings to create a constant current will help to minimize power loss. 

You’ll want about 4 ohms of resistance when the windings are “cold,” but this can change if the windings warm up or expand and short.

Pulley bearing failure

When Power Take Off (PTO) is engaged the pulley on top is rotating the same speed as the crankshaft. When you turn PTO “Off” it should stop, but there will likely still be momentum that needs to be used up. 

There are springs into the clutch that pull the clutch back against the metal housing and act as a “brake”. When you turn on PTO, you apply windings’ magnetic force that overcomes springs. 

The clutch engages due to this Turning your PTO off is easier than you think, and unlike not using the tool at all, this also prevents the blades or whatever else from free wheeling.

Symptoms of a bad PTO clutch

A common sign that your PTO clutch is going bad is when you have the lawn mower hardly turns over but not starts. You also can experience strange noise in your lawn mower that might have been created due to the bad PTO clutch.

The engine is hard to start

There are a number of factors which contribute to the symptoms of a bad clutch. 

A common symptom is taking time to engage. When your lawn mower starts to give you trouble and is hard to start, it might mean that there are problems with the PTO clutch. An engine will take several seconds for its blades to engage. 

Furthermore, it can get hot after running for a while. Here are some fixes to this issue:

  1. Refreshing the air filter and cleaning it increases engine performance
  2. Checking all wiring increases engine performance
  3. Checking the carburetor increases engine performance
  4. Adjusting the carburetor decreases engine performance

Squealing noise when engaging or disengaging

Noise while starting the engine might be a symptom of a bad PTO clutch. When the clutch engages and disengages, noise is made from the worn-out input shaft bearing as it moves back and forth inside the engine. 

A noise can also be caused by worn-out input shaft bearing that needs to be replaced. A worn-out input shaft bearing can be fixed by replacing it with a new one or by greasing and reseating the bearing again in its original position.

Noise can be a great way to detect a broken PTO clutch or any other problem with the PTO clutch. It makes noise when turning the key by disengaging and turning off and on the engine several times. 

If you hear a squealing noise and your power shuts down, it might be indicating that the PTO clutch galled or a jammed slip ring.

Clutch won’t get power and engine won’t turn over

When the clutch won’t engage, it means that the PTO solenoid is defective. For this reason the clutch won’t get power to run properly. This solenoid needs to be replaced if there is no power getting to it. 

If the engine isn’t getting power, then the switch is malfunctioning and needs to be replaced as well.

Bad PTO clutch switch
Bad PTO clutch switch

To fix this issue, try to depress the brake pedal. If the pedal is not depressed, clean the terminals of your battery. If this doesn’t fix it, replace/check your starter or solenoid as they can sometimes fail to work properly.

How to test a PTO clutch?

  1. Carefully examine the clutch drive assembly.
  2. Read the volts. If you find the voltage is lower than 12.4V, then you have to recharge the battery as it won’t start without proper power.
  3. The in-line fuse should be checked after that. Ampere fuses are replacements for blown fuses. If the original fuse is black or blown, use the same ampere fuse rating as the original
  4. Start the engine and check the blades to make sure they’re operating smoothly. If you hear anything, get a new ignition key or disconnect the battery before checking any further.
  5. Make sure that there are no broken branches jammed into the pulley.
  6. Again, plug in the ignition key, negative cable, and socket. Turn on the clutch engagement lever, and disengage it when the engine has started. Turn it on and off a few times. The pulley slows down and stops frequently might be a sign of a bad PTO clutch.
Testing a PTO clutch
Testing a PTO clutch


We’ve discussed several things for you to understand the symptoms of a bad PTO clutch. Hope this article will help you to understand if your PTO clutch is working bad. If your clutch is too bad, you might have to replace the component with a new one.

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