John Deere Mower Blades Won’t Engage: Troubleshooting Guide


A riding mower makes it a cinch to keep large lawns manicured and pristine – at least, as long as the machine works as it should. Blade engagement problems prevent the tractor from cutting the grass properly (or at all).  When it comes to John Deere mowers, the problem is often linked to the electric PTO. Models often affected by this issue include the E100, D130, I130, I110, and X300. However, the power take off clutch is not the only culprit.

More often than not, the John Deere mower blades won’t engage because of a faulty PTO clutch. The PTO switch may also be defective, or the problem could be a broken drive belt or pulley. Dirt and debris blocking the blade may also keep it from engaging.

Why Blades Won’t Engage On John Deer Lawn Tractor

Trying to mow a lawn just to discover your John Deer lawn mower blades won’t engage is frustrating. There are several potential culprits. Let’s check them out and see how to troubleshoot your machine.

Most Common Culprit: PTO Clutch

The power take off (PTO) clutch is a mechanism that allows you to disconnect the power coming from the motor and engage or disengage the blades on-demand. This mechanism is either manual or electric. An electric PTO clutch runs on batteries that can drain or break over time.

Thus, the first thing to check is the power source if your lawn tractor has an electric PTO clutch and the blades won’t engage.

If the battery works fine, you should check the clutch and see if you have to replace it – PTO clutches can’t be repaired, but replacing a defective component is fairly easy. Here’s how to check the clutch.

1. Test the battery

Use a lawn mower lift or floor jack to lift the front of the tractor. Make sure you have enough clearance for working under the deck.

Find the clutch and battery under the deck – you may have to read your vehicle’s manual to find the exact location – then use a voltmeter to measure voltage. If the voltmeter reads 12.5 volts or below, you have to replace the battery.

2. Test the fuse 

If the battery works as it should, the problem could be the fuse. The PTO fuse is located inline between the clutch’s switch and the clutch assembly near the deck. If the fuse is black or has a blown filament, you have to replace it.

3. Check the clutch

Inspect the area under the deck and make sure it’s free of debris. Disconnect the power wires that go to the clutch assembly and check them with a test light. Use the same method to test the PTO switch, and then check the clutch with a multimeter – the resistance should be between two and four ohms. Replace the switch, wires, or batteries if needed.

PTO Clutch Related Issues 

A broken PTO clutch can’t be repaired, meaning that you have to replace it. However, the part isn’t cheap, so you should check out all other potential issues before spending your hard-earned money.

Obstructions

A PTO clutch controls the power flow from the mower’s engine to the blade and is located under the deck. Grass clippings, twigs, and other garden debris can sometimes jam the clutch mechanism.

The issue is a breeze to fix. Lift the riding mower’s front and inspect the area under the deck. Make sure the mower is turned off (you should disengage the battery to stay on the safe side) and pull out larger debris that is stuck under the deck or around the clutch.

You can also wash off debris with a garden hose or power washer to remove caked mud and stuck grass clippings.

Defective Clutch Solenoid 

Solenoid coils are robust and reliable, but they can fail due to a number of factors.

Incorrect voltage is one of the most common culprits, a too high voltage burning the solenoid. Likewise, too little voltage won’t deliver sufficient power.

Contact with water is also detrimental. While wet debris could make its way to the clutch, you should keep the area clean to prevent damage.

A burnt solenoid can’t be repaired, and you’ll often have to replace the entire PTO clutch to fix the issue.

Worn-Out Clutch

Like all mechanical or electrical components, your mower’s PTO clutch will wear out in time. Cracks in the clutch’s casing are the most frequent problem. These cracks can lead to oil loss and, eventually, cause a transmission problem.

Worn-out clutch plates can also fail to engage or disengage the blades. The only fix is to replace the clutch.

Broken Wires 

If the clutch, battery, and fuse are all working properly, the issue could be a broken wire. Inspect the wires going from the switch to the clutch and motor. Repair any wires that have come loose or that are broken, then try to engage the blades again.

Installation Issues 

Sometimes, you may notice that your John Deere mower blades won’t engage after you’ve replaced the old clutch with a new one.

The problem is likely caused by installation issues. It is crucial to follow the instructions in your user manual when replacing the PTO clutch – or any other components, for that matter – because improper installation could lead to permanent damage.

If you suspect any installation issues, remove the clutch and test it for functionality. Also, test the fuse and battery. If everything works properly, install it again following the steps in your mower’s manual. Alternatively, have your mower serviced professionally.

PTO Switch Problems

Also called the blade engagement switch, the PTO switch tells the clutch that it’s time to turn the blades. If this component is defective or if it has loose wires, it will fail to supply power to the clutch, and the blades won’t spin.

How To Test a Defective PTO Switch

1. Check electric continuity

All zero turn mowers and riding mowers use the same type of PTO switch with two full rows of pins (three on each row) and a row with two pins.

A properly working PTO switch has electric continuity only between the first and third pin on each 3-pin row, when it is turned off. You shouldn’t detect continuity between any other pin combination. Test continuity with a multimeter.

If all seems right, turn the switch on (the knob pulled out) and test continuity between the first and second pin on each row (including the row that only has two pins). Keep in mind that you should have no continuity between the rows.

If you have continuity between any other pins or between one row and another, the switch is bad and has to be replaced.

2. Check resistance 

If your switch has passed the continuity test, it’s time to check the resistance (measured in ohms). Turn the switch off and use the multimeter probes to check the resistance between the first and third pin on each 3-pin row.

Do the same with the switch on, testing the resistance between the first and second pin on each row (including the 2-pin row). The resistance should be zero or no more than 0.01.

If the resistance is higher than 0.01 or the multimeter reads OL, the switch is bad, and you have to replace it.

Pulley Problems

To engage and disengage the blades, the PTO clutch is connected to a pulley that controls the tension in the drive belt. This pulley should rotate freely when the clutch is disengaged and apply tension to the belt when the clutch is engaged.

Debris blocking the pulley, another jam, or a damaged belt could prevent the pulley from rotating. Thus, the blade will not engage.

The first step to fix the issue is to check the area under the mower deck and clean all debris. Also, check the belt and replace it if necessary. Alternatively, replace the pulley.

Drive Belt On Tractor’s Deck

Another potential culprit could be your lawn tractor’s deck drive belt. This drive belt connects the motor to the deck. If it is too loose, damaged, or worn out, it could fall off and prevent the blades from engaging.

Check the drive belt and tighten it if needed or place it back in position if it has snapped out. If the belt is worn out or damaged, replace it.

How To Engage Blades On John Deere Riding Mower

The John Deere lawn tractor drive system is similar to the systems used in other riding or zero-turn mowers. The PTO clutch in the lawn tractors from the brand is located between the deck, and it’s easy to engage either manually or by pressing a switch. Let’s see how to command the blades to turn depending on the lawn mower you’re riding.

Mechanical System

While electrical PTO clutches are slowly gaining popularity, the mechanical system is still the most common type found in John Deere’s utility vehicles.

To engage a mechanical PTO clutch, you have to slide a pulley in position by moving the PTO clutch lever. When the lever is in the engaged position, it creates tension in the mower deck belt. Power from the motor combined with the belt tension causes the blades on your riding lawn mower to turn. Here’s how to engage the blades:

  1. Turn on the riding lawn mower and advance the throttle to half-speed. Let the motor warm up for a minute or two.
  2. Raise the mower deck to the highest setting. Check for debris and remove any grass clippings or twigs. When clean, lower the deck to the desired cutting height.
  3. Push the PTO clutch lever (on the right side of the steering wheel) all the way forward. The blades should spin now.

Electric System

Essentially, the electric PTO clutch works just like a mechanical one, but instead of pushing a lever, all you have to do is press a switch.

When the switch is on, it sends a 12-volt current to the clutch and enables a brake with a pulley under it. When engaged, this pulley engages the mower drive belt, and the blades start spinning. To engage an electrical PTO clutch:

  1. Turn on the riding lawn mower and advance the throttle to half-speed. Let the motor warm up for a minute or two.
  2. Raise the mower deck to the highest setting. Check for debris and remove any grass clippings or twigs. When clean, lower the deck to the desired cutting height.
  3. Pull up the PTO switch located to the right of the steering wheel (the switch could be red or yellow, depending on the riding mower you have).

FAQs

Should the PTO pulley spin freely?

Yes, the PTO pulley should spin freely when the clutch is disengaged. An obstructed movement can prevent the pulley from delivering enough tension to the drive belt and prevent the blades from spinning.

How often should mower blades be sharpened?

You should sharpen your riding lawn mower blades every 25 to 30 hours of use, which is about twice per season, and every time they’ve hit rocks or other hard obstacles. Inspect the blades after each mowing if your terrain is rocky because the stone can chip or dent the blades.

Can you bypass a PTO switch?

You could bypass a PTO switch by running a wire from the key switch to the PTO clutch solenoid through the brake switch. The task isn’t complicated if you have minimal electrical and vehicle repair skills, but it could be dangerous.

By bypassing the PTO switch, you’ll engage the blades each time you start the mower. If the deck is raised and there are small pets or little hands under the mower when you start it, you could injure your child or furry friend.

For this reason, you should replace a broken PTO switch as soon as possible rather than bypass it.

Final Thoughts

The PTO clutch or switch are the most likely culprits when lawn mower blades are not engaging. Before troubleshooting, check the deck and remove all debris blocking the blades, clutch, or drive belt. We hope the guide above can help you deal with all potential issues.

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