John Deere Lawn Mower Blades Will Not Engage [3 Easy Solutions]

You have an L120 Lawn Mower from John Deere and you have used it for the last five years. Since then, it works efficiently- except yesterday. When you turn on the mower, you find its blade won’t engage. 

If this is the case, we recommend you inspect the belt of the mower on the deck. If the belt is in its place, we bet the PTO switch and the PTO clutch are at fault. Due to these damaged parts, you can never engage the mower blade. 

Below, we will break down why the John Deere Mower blades won’t engage. So, keep reading between the lines to explore the solution. 

John Deere Lawn Mower Blades Will Not Engage

In this chapter, we will let you know the reasons that cause your mower blade to not engage. On top of this, we also provide the troubleshooting steps to fix those issues. 

01. Defective PTO Switch

The PTO switch can be the main culprit if the lawn mower blades won’t turn or rotate. If it gets defective, this switch fails to supply power to the PTO clutch. Consequently, the PTO clutch will not engage, which also causes the blades to not rotate. 

There are several reasons behind a faulty PTO switch. Bad electrical connections and corroded terminals are some caveats for erratic PTO switches. Loose wire connection between PTO switches and PTO clutches is also responsible for a malfunctioned PTO switch. 

How To Fix: 

Firstly, check the wiring from the PTO switch all the way down to the PTO clutches. If you find the wiring loose, tighten it up. Don’t forget to inspect the wiring for damage. If the wire harness gets damaged, you need to replace it. 

Once you check for loose or damaged wiring, it’s time to check the PTO switch itself. Testing this switch for continuity is simple. Just pull the hood from your lawn mower. Then, go under the dash and pull the wire harness that is attached to the PTO clutch. Grab the whole plug and pull it down. 

Now, what you need to do is- squeeze the tabs on the PTO switch and pull the whole switch up. Once you remove the switch, connect it with a multimeter to read the continuity. If you attach the two leads of the multimeter to the top & bottom plugs, your multimeter will beep. It means the switch is okay. Otherwise, understand the switch is defective if the multimeter doesn’t beep. 

If the PTO switch is defective, just replace it with a new one. Get a new switch, and attach it to the PTO clutch wire harness. 

John Deere Lawn Mower Blades Will Not Engage

02. Faulty PTO Clutch

A defective PTO clutch also prevents the lawn mower blades from engaging. Now, you may ask- how can I know whether the PTO clutch is working or not? You can test it without running the actual lawn mower by engaging the PTO switch with the battery on & the motor off. 

You will hear a click when you flip the PTO switch. If you don’t hear the clicking noise, check the battery. A low-charge battery fails to provide sufficient power to engage the PTO. Use a voltmeter to read the battery output. If the readout is 12.5V, the battery is fine. If needed, charge the battery. Now, turn on the PTO switch again to hear the click. If you can’t hear the click, you need to replace the PTO clutch. 

How to Fix: 

PTO clutch is not repairable. It means you need to replace it with a new one when it gets damaged. If you don’t know how to remove & replace the PTO clutch of your John Deere Lawn Mower, check out this tutorial

03. Belt Gets Stretched or Loose 

The mower blades won’t engage if the belt gets stretched or loose. When the belt gets loose, it will snug or fall off completely. If you are trying to process too much grass, the leaves or grass may accumulate under the deck and push off the belt. 

How to Fix:

If the belt gets loose, adjust its tightness. In other cases, you need to replace the belt. You can watch this tutorial to learn how to replace a mower belt. 

Related: Husqvarna Riding Mower Blades Won’t Engage

How Do You Engage The Blades On A John Deere Lawn Tractor?

How you engage the blades on a John Deere Lawn Tractor depends on the type of blade engagement you have. 

If you have a mechanical blade engagement, turn the key to the on position first. Then, allow the engine to warm by accelerating the throttle to half-speed. 

Next, position the mower to your desired cutting height and ensure there is no debris around the mower. 

Finally, it’s time to engage the mower blade. To do this, kick (push) the lever to the right of the steering wheel forward fully. 

On the other hand, if the mower has electric blade engagement, do the same thing we mentioned- except the final step. In case of electric blade engagement, you just need to pull the PTO switch up to the right of the steering wheel. 


What is a PTO switch?

A PTO switch works as a lever often found on mowers & tractors. The full meaning of this acronym ‘PTO’ is Power Take Off. It can be either an electric switch or mechanical, which takes the engine power to run the mower deck. It generally runs the mower with the help of the belt or shaft. 

Where is the PTO switch on a John Deere mower?

You can find the PTO switch on the dashboard of most John Deere mowers. The color of the switch can be red, yellow, or blue. 

What would cause a PTO to not engage?

The PTO won’t engage due to these two reasons- faulty installation and misuse of the PTO. 

Lawn mower troubleshooting relevant articles –

Lawn Mower Starts with Starter Fluid then Dies

Why is My Lawn Mower Blowing White Smoke?


John Deere Lawn Mower Blades won’t engage because of a defective PTO switch, a faulty PTO clutch, and the belt getting loose or falling off. Fortunately, we mentioned the troubleshooting steps to fix these issues. 

As a bonus, we also described how to engage lawn mower blades on a John Deere. After trying all these steps if you can’t engage the mower blades, don’t hesitate to call a service guy. 

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