John Deere LX188 stalls when brake pedal is released

[Bighorn2500]

Looks like the brake switch went bad that is supposedly near the hydrostatic trans from what I've read. I was mowing and it died but was able to restart with the brake pedal pushed in but as soon as I let off to push the forward pedal it stalled.

Is that the only switch I'll need to replace? Still need to remove rear fenders to access and get a part number off of it to order a new one.

 

[NormanBuntz]

Maybe try Jack's Small Engines website. Good diagrams.

 

[Geauxtiger]

Sounds to me like you may have a seat switch problem. With brakes applied, typically the seat switch is by passed (for example, if you need to get off the mower for a moment and keep the engine running, you typically need to set the brake). Once you release the brake, the seat switch becomes 'active' (maybe there are more switches that become active also?), so if the seat switch, or its wiring is bad, releasing the brake would cause a stall.
The seat switch is always active when the blades are running. The fact you stalled while mowing also leads me to a seat swtch/wiring issue.

 

[JTK]

If it's not the seat switch, it could be the PTO safety switch. I'd jumper each for troubleshooting.

 

[mk378]

Yes almost certainly the seat switch, which is designed to kill the engine if you leave the seat while either the drive or the blade is engaged.

 

[Bighorn2500]

Looked last night, seat switch is jumpered out already. So I'll move on to the switch near the rear axle that ties into the brake pedal.

 

[mk378]

From looking at the schematic, if the seat switch is closed (seat occupied), the ignition is always enabled regardless of the other interlocks.

So double check that rigged jumper. The pink wire to pin 8 of plug X4 on the interlock module is the output of the seat switch, it should be live whenever the key is on and seat is occupied (and / or seat switch jumpered).

 

[passgas55]

If the seat switch bad then would not the mower start? After thinking about it it will run if the brake pedal is locked in and you get off the seat. When you release the brake then the seat switch comes into play.

 

[mk378]

On this particular machine the engine can be started and will keep running as long as the brake is on and the PTO (mower blade drive) is off, even with the seat not occupied. To keep running after releasing the brake or engaging the PTO requires the seat to be occupied.

Also it is required for the brake to be on and PTO off for the starter to work.

 

[bubbatime]

I just bought a used riding mower today, that dies when you put it in reverse if the blades are engaged. That HAD to go. Its hard trying to mow the grass if you cant back up. I found the plug for the reverse safety switch and unplugged it. Now it works fine and can back up with the blades still spinning without killing the engine.

So methinks you need to check your seat switch and your reverse safety switch.

 

[gman2304]

Originally Posted by mk378
On this particular machine the engine can be started and will keep running as long as the brake is on and the PTO (mower blade drive) is off, even with the seat not occupied. To keep running after releasing the brake or engaging the PTO requires the seat to be occupied.

Also it is required for the brake to be on and PTO off for the starter to work.
^^^ This is how the safety switches work on the LX188. I bought one new in 1998 and it's still my go to mower.

 

[Geauxtiger]

Originally Posted by gman2304
Originally Posted by mk378
On this particular machine the engine can be started and will keep running as long as the brake is on and the PTO (mower blade drive) is off, even with the seat not occupied. To keep running after releasing the brake or engaging the PTO requires the seat to be occupied.

Also it is required for the brake to be on and PTO off for the starter to work.
^^^ This is how the safety switches work on the LX188. I bought one new in 1998 and it's still my go to mower.


Yup. Same with my JD LX277. I also have a Snapper zero turn that has the same logic. Think most modern machines are the same.

 

[Bighorn2500]

Replaced the brake safety switch that's threads into the hydrostatic trans yesterday and it runs now with the brake off. Checked all the other connections and put some dielectric grease on the terminals after cleaning them. Mowed for about an hour last night without issue.