PTO stopped working...seat switch or TDC?

[v8only]

So my 755 PTO stopped working i have been trouble shooting and I believe its the TDC module. One thing i noticed is that the magnet was disengaged when the pto lever was engaged when i physically held the magnet in place the PTO operates.

Does this make sense that the TDC Module would cause this issue?

Also when I pull up on the seat switch to override the switch the magnet energizes and PTO works.

Thanks.

 

[JD755]

The seat override switch will only operate the rear PTO. When override is engaged, it provides direct power through the PTO Rear Only Selector lever to the magnet. The TDC module is not involved with that operation. I assume when you said the override works, it was to operate the rear PTO.

Since your magnet has been shown to work using override, the problem could still be the other normal operation side of the seat switch, or the wiring, or the TDC.

 

[Mechanos]

Like JD755 stated, you know the magnet is good. Next step is to remove the left side panel of the operators station to gain access to the TDCM. Unplug the module and install a jumper wire from the Yellow wire to the Blue wire on the tractor side of the harness plug. If the PTO now works, the TDCM is bad. If it does not work, the next step is to jump the seat switch. If the PTO now works, the problem is the seat switch... if it does not, then the problem lies in the wiring harness.

 

[v8only]

thanks JD755 & Mechanos i will check that out tonight.

To get this clear you mean jump the yellow wire from the seat switch to the blue wire on the TDCM?

 

[v8only]

update:

Today i finally got my new seat switch but JD only carries one style of seat switch it only has yellow and red wire but has 2 other prongs that i guess can be set up like the factory switch with 4 wires, yellow pink yellow and blue. JD informed me to use the switch as is with only the yellow and red.

So i put it in and the rear PTO engaged who hoo.

About an hour in i shut down the tractor stopped for supper, went back out and engaged the PTO and the magnet did not engage, i got off the tractor and depressed the new switch as if i was sitting on the chair and it still did not engage. So i was approaching the garage to open it and start to trouble shoot hopped on the tractor went to engage the PTO and it worked.

So i finished my job and hopped off to refill the tank and again the same problem so i noticed that the more i would jump on the seat the pto would engage, once engaged i could engage and disengage and engage via the switch no problem but if i got off the seat it would not engage unless i really bounced on the seat.

Any ideas where to go next? I am thinking that i should wire the new switch like the old switch considering it has the prongs for it only thing that worries me is that the new switch does not pull up to over ride.

 

[JD755]

First. Did you do the test to bypass the TDCM?

Second. Your problem may not be electrical, but instead mechanical. Every time you attempt to engage the PTO, you are moving the lever toward the magnet. Sometimes it engages, sometimes not. There have been others here with a problem where the magnet slightly moved out of position to where it could not always hold. An adjustment of the magnet may be required.

 

[v8only]

yes i did the test to bypass the TDCM and it tested fine.

Do you think it has anything to do with the new seat switch not having the blue wire connected making it intermittent?

I do not think the magnet is at fault as i have watched the magnet and there is no room for adjustment the magnet and lever plate touch and the magnet moves freely with no binding. But i will check this anyways.

Also where is the black ground wire for the TDCM i have followed the wires up and cannot see where it goes. Does the TDCM ground through the module on the block?

 

[JD755]

The blue wire to the standard factory switch is only used for the off-seat bypass function. I assume you have no need to operate rear PTO implements while off the seat, such as a log splitter. Does the new switch have a manual pull-up off-seat mechanical position?

Have you tried to bypass the seat switch full-time? Meaning just leave it bypassed while operating the tractor. Not good for safety long term, but OK for testing purposes. When it does work, have you tested the module timing? When you are on the seat the PTO remains engaged. If you just very briefly raise up does it stay engaged? It should, but anything long than just a brief bounce off the seat should shut off the PTO.

The switch is mounted on a long metal tab. Are you sure the tab is positioned and stable so the seat firmly pushes the switch on and the tab down slightly?

 

[jd3x]

yes i did the test to bypass the TDCM and it tested fine.

Do you think it has anything to do with the new seat switch not having the blue wire connected making it intermittent?

I do not think the magnet is at fault as i have watched the magnet and there is no room for adjustment the magnet and lever plate touch and the magnet moves freely with no binding. But i will check this anyways.

Also where is the black ground wire for the TDCM i have followed the wires up and cannot see where it goes. Does the TDCM ground through the module on the block?

I had a PTO problem, the fix was the ignition switch. There is a relay on this module that controls the PTO function.

Good luck,
Jd3x

 

[v8only]

the new switch does not have the manual pull up off the seat position therefore i guess i no longer need the blue wire.

i have bypassed the seat switch using a jumper wire from the red wire to the yellow wire and the PTO operates continuously, I have also tested the module timing the PTO will operate when sitting on the seat i will raise up for 2 seconds and the PTO will disengage. I have also pulled up the long metal tap to ensure i get good contact on the switch, however i have ruled this out because when i push the switch down by hand and try to engage the PTO it will not work.

I am starting to gather all of the information here in my head and i am starting to think it maybe a weak magnet or a bad ground somewhere. Where is the ground for the PTO operations? I will go through all of the testing procedures when i get home from work today and see where i get.