# John Deere 850 was hot wired trying to fix it back correctly



## Dimondaigle (Dec 15, 2020)

Can someone please help me with a diagram for the Alternator and starter wiring also don’t know if the there is a good diagram to the Ignition switch


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## bmaverick (Feb 20, 2014)

You came to the right tractor forum. 

Up at the top is a section called MANUALS. Click it.

Next look left and click TRACTOR.

Net click CUT.

In this section, scroll and grab every PDF related to a JD 850. I uploaded a bunch. 

These are all FREE. 

I also have a TM1192 850 900HC 950 1050 Technical Manual.PDF, but it's 50Mb and too big yet to put here. Shot a me a PM to get it too.


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## Dimondaigle (Dec 15, 2020)

I don’t see how to PM you for the 50mb Technical Manual please send it to me


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## bmaverick (Feb 20, 2014)

Dimondaigle said:


> I don’t see how to PM you for the 50mb Technical Manual please send it to me


PM is a private message you send from this forum. This way, your email contact info is not displayed to the world and not out there for spambots on the web to flood your inbox.


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## pogobill (Jan 31, 2012)

Dimondaigle said:


> I don’t see how to PM you for the 50mb Technical Manual please send it to me


Just click on the users name under their avatar and select "start a conversation"


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## bmaverick (Feb 20, 2014)

pogobill said:


> Just click on the users name under their avatar and select "start a conversation"


That will work. 

We're getting it done.


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## bmaverick (Feb 20, 2014)

Dimondaigle said:


> Can someone please help me with a diagram for the Alternator and starter wiring also don’t know if the there is a good diagram to the Ignition switch


So, what s/n is on the tractor. Look near the PTO output shaft for an ID plate. 

There is a late model and a recent model in the s/n production of this machine. It will help to know which schematic you will need.


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## Dimondaigle (Dec 15, 2020)

The tractor starts but I have to start it by pressing wire on the starter post and it’s very aggravating I’m trying to be able to wire it to start from the key ignition I just purchased it for a good deal The people that had it said they lost the key so that way they hot wired it but I went down to the local dealer and purchase 2 sets of keys for 15 bucks and it does fit into key ignition and it turns but not starting that way and I’m trying to start off right not to mention the wifey will love to just jump on it and go but she will not deal with it like this!! the 2 white wire coming from A From Alternator one of the wire was cut the other one looks to be ran all the way to the key ignition so the one that was cut coming from alternator was not going to starter so I tied in some wire and ran to starter and tried to start by key but still didn’t work I just used some extension cord wire Is it possible that there is not enough voltage using these rigged up way im so lost at this point please help me get this thing wired right what should I do next and if I should check any fuses??


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## bmaverick (Feb 20, 2014)

The s/n really helps to sort out your dilemma. With an early JD850 and a later JD850 based on the s/n changeover, the correct wire-harness schematic can be used to successfully get your machine going. 

You are looking for a plate on the tractor like this one. 1-1/2-inch tall by about 4-inches long. IT site right below the PTO output shaft. IF none is there, you'll have to 'guess' the year it was made and hope it's right. 
This is the OLD style and early ID plate. This came off my actual JD850. 
It was a 1979 model. 









Here is the newer model ID plate just under the PTO output shaft. 
S/N shows it was made in 1985. 









The ID plate under the PTO output shaft is a dumb place to put it. How many times does a PTO shaft whack that area when hooking it up? Hundreds of times.  

Tractor Data use to show the s/n split on their page for the JD850. It's not there anymore. hmmm.
http://www.tractordata.com/farm-tractors/000/0/9/99-john-deere-850.html 
*850 Serial Numbers:*
Location: Serial number plate on the rear of the John Deere 850, below the PTO shaft.
1978: 1000
1979: 3859
1980: 7389
1981: 11338
1982: 12481
1983: 14183
1984: 16006
1985: 18001
1986: 22001
1987: 25501
1988: 28337
Final: 30852 

Near the starter is the engine plate. This came off my actual JD850 too. 
Above the engine ID plate, the block typically has a 3T80J XXXXX number after it.
I would assume a low number would mean it's the OLD style JD850. It's the only other clue I can think of at the moment.


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## bmaverick (Feb 20, 2014)

The TM1192 Section 40 & 240 (pg-625+) is your primary focus.

For the schematics, I have these.
And look at the attached PDF. (important)
There are 2 schematics both labeled the same, 850/950/1050 aka YM2500/ /YM4300


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## bmaverick (Feb 20, 2014)

BTW, you can pay $$$ going to your JD dealer or just order from a Yanmar YM-Series parts supplier for 1/3rd the costs. 

Fredrick's Equipment
JD850 aka YM2500
https://fredricksequipment.com/product-category/ym-series/ym2500 
https://fredricksequipment.com/product-category/john-deere/850 

Hoye Tractor Parts
JD850 aka YM2500 
https://www.hoyetractor.com/CTGY/2500.htm
https://www.hoyetractor.com/CTGY/JD850.htm 

Key is less than $5 or $8. 
https://fredricksequipment.com/product/ignition-key-flat-steel-for-original-ym-switch-ik-5216/
https://www.hoyetractor.com/PROD/YMKEY55-F.htm

Here is my JD850 key along side my YM2500/YM2610 key. SAME, SAME.


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## bmaverick (Feb 20, 2014)

Dimondaigle said:


> The tractor starts but I have to start it by pressing wire on the starter post and it’s very aggravating I’m trying to be able to wire it to start from the key ignition I just purchased it for a good deal .... what should I do next and if I should check any fuses??


You need to TEST the ignition switch. And the fuses are on the left side under the dash. Or just look at the clutch pedal and then follow straight up.

With the glass fuses, you can easily test them without pulling them out. Use a volt meter and check for continuity on each end.


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## Dimondaigle (Dec 15, 2020)

The only plate on my tractor is this and I called John Deere and they said they don’t find anything on this number they directed me to local dealer which was no help cause they didn’t find anything either don’t know if maybe Yanmar can help if anyone can find something on this engine s/n and model it would be very helpful


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## bmaverick (Feb 20, 2014)

Page 649 ...


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## bmaverick (Feb 20, 2014)

Dimondaigle said:


> The only plate on my tractor is this and I called John Deere and they said they don’t find anything on this number they directed me to local dealer which was no help cause they didn’t find anything either don’t know if maybe Yanmar can help if anyone can find something on this engine s/n and model it would be very helpful


That's the engine model plate. AND .... It tells me your JD850 is the newer type and a higher s/n if it had one. Look at that engine plate, it has RAISED numbers and not stamped into the plate. Issue solved. 

So, with this info you should use Fig 11 for the schematic.


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