Need help identifying electrical part on John Deere 850 tractor

[Quattro]

An in-law has a John Deere 850 compact tractor on his ranch and has had intermittent starting problems over the last couple of years. This weekend, after much diagnostic circuit testing and jumping across various electrical terminals we determined that it wasn't the battery, and that if power was jumped to the starter solenoid terminal directly from the battery or the starter terminal on the start switch the tractor would start. Sounds like a safety switch issue but they've all been bypassed.

We stumbled onto the fact that when the tractor won't start (not even a click from the solenoid) there is a rapid clicking noise from an electrical box that sort of resembles a generator voltage regulator, and if your pounded on this box with some suitable object while holding the key in the start position the tractor would start and continue to run. This box is located in the dash, on the right side, just behind the dash panel. It has a six wire connector on the front.

What the heck is his box? I've burned up hours on the internet looking at parts diagrams and lists of electrical parts for this tractor and I can't find it. I spent a fair amount of time on John Deere's site looking at their parts diagrams for this tractor and I couldn't find it. The clicking noise would seem to indicate that it's some sort of relay, or box of relays.

Unfortunately, I won't be back on this ranch until after Thanksgiving, so I can't provide any more information at this point

Thanks,
Quattro

 

[JD755]

Is this the box?

 

[Quattro]

Is this the box?

YES. Thanks so much for your help.

It looked like a voltage regulator but it seemed like an odd place for it, and I thought that this tractor would have had an alternator with a solid state regulator located nearby.

Any ideas why it would cause an open or short in the starting circuit? Once again, when this thing fails to start, there is not even a click from the starter solenoid, even with a new battery.

Do you know the part number? I have already spent a lot of time Googling "John Deere 850 voltage regulator" and all I got was multiple instances of the solid state/heat sink looking gizmos that I associate with modern alternators - nothing that looked like the regulator in the tractor and in your posting.

Quattro

 

[JD755]

If you sign up on JDparts.com, you can look up all those parts. You can also see the (usually high) prices.

Your CH12806 regulator is $233.53.

BTW, welcome to TBN!

 

[Dirtdeere]

Check the battery cables first. I had the same problem and it was the positive cable. It clicked like yours is doing. Turn the key a shake the cable around. I've seen this prob twice on these tractors. Good luck!

 

[Quattro]

Dirtdeere,

Thanks for chiming in, but, as stated above, "there is not even a click from the starter solenoid" when this tractor refuses to start. Lots of juice to the starter motor terminal and to the start switch, but there's a problem getting current from the start switch to the solenoid terminal. We "hot wired" the solenoid terminal on the start switch to the solenoid, and the tractor would start with the key and run fine. Sort of an awkward arrangement to live with, though.

Quattro

 

[Quattro]

JD755,

Thanks again. I had been on that site and looked at that diagram and it didn't register with me, probably because the regulator in this tractor does not have a pigtail - the six wire connector is part of, or should I say sticks out of, the regulator housing.

Interestingly enough, when I Google the part number you provided, CH12806, all I get is solid state regulators that look nothing like the tin box that's in this tractor or the unit pictured in the JDparts diagram. I wonder if they changed from a mechanical to a solid state regulator on the 850 at some point?

 

[JD 4520]

Try jumping your tractor from your car or truck. See if this works. If it does, you don't have enough cranking amps but you have voltage.

 

[vwnotrunning]

I would venture that part is not in the starting circuit. You may be just moving a loose connection in the safety circuit or the fuse box. On our 1050 has an intermittent problem with one of the neutral safety switch. When it is not making contact it is just like you are describing.

 

[JD755]

JD755,

Thanks again. I had been on that site and looked at that diagram and it didn't register with me, probably because the regulator in this tractor does not have a pigtail - the six wire connector is part of, or should I say sticks out of, the regulator housing.

Interestingly enough, when I Google the part number you provided, CH12806, all I get is solid state regulators that look nothing like the tin box that's in this tractor or the unit pictured in the JDparts diagram. I wonder if they changed from a mechanical to a solid state regulator on the 850 at some point?

With some further research I see there were earlier versions of the regulator. Those were replaced by the CH12806.