8450 electrical problems

[Dale36]

Ive got a little problem Im hoping someone can possibly help me solve. Anyway, I have been looking for the power wire to my fan switch. Fan stopped yesterday and it has no power coming to the switch. The wire has power at the load center just not at the switch. So I figured it was a loose or corroded connection somewhere in the harness. Got my manual out and started looking at how it was ran, of course my manual is not showing even remotely close to the way the wiring is on this tractor. It shows 3 (I think) connections on the firewall, mine has nothing on the firewall just harness runs through and starts splitting off to a bunch of big flat connectors and 2 round ones. Long story short I took all the connectors apart and cleaned them and put them back together. Didnt help my fan but boy did it mess up the gauges and lights on the investigator ll ! All gauges except alternator are pegged and wont go back to normal. I took the 2 round plugs back apart and was fooling with a test light trying to figure something out and when I touched certain pins or holes each gauge would return to normal. So I figure its a ground problem somewhere but Ive checked all the grounds I have found and they seem to be alright. My manual is a tm1255 dated dec82 (tractor is 82 model)until you get to the electrical schematics then it goes to feb85. I guess they changed the wiring on the later models or somebody changed it on this tractor anyway. So if anybody has any ideas as to where to look for a ground problem or something else I should look for Id appreciate it, or maybe someone has a wiring diagram for this year model 8450 thatd be great too! Sorry for rambling but any help would be greatly appreciated, thanks!

 

[Jim.ME]

The John Deere Ag Bookstore shows the 8450 has two Technical Manuals, both are needed for proper coverage of things. The same two manuals apply to all the 8450s, even though there is a serial number break at <5500 and 5501>, the difference is in other manuals they show for the later tractor group.

TM1256 is the Operation and Test Manual. TM1355 is the Repair manual. (As TM1255 a typo? Is yours an OEM manual or reprint from a third-party vendor? A search in the JD Ag bookstore did not turn up a TM1255.) If these are like the two manual sets, I have worked with most of the electrical system function and diagnosis is in the Op & Test manual and the Repair manual gives info on repairing/replacing components.

There is a phone number on the home page of the bookstore which you could call and ask about what is included around the electrical system in each manual. You can go to the bookstore, click on Equipment Publications, and do a model search by putting 8450 in the box and searching. that will let you see the manuals available. Here is a link to the bookstore.

https://techpubs.deere.com/

 

[Tx Jim]

Remove access panel in front of dash on LH side & be sure all nuts are tight on circuit breakers. Check operation of accessory relay(item 31)

 

[Dale36]

Thanks for you reply! No typo, I have a tm1255 that is genuine
John Deere and also have a tm1355 that was purchased through
an online pay to print type deal and it was geared more towards
the 8650 engine wise anyway it didnt have much in it about the
466. Everything that I have worked on so far has been step by
step perfect in the 1255 manual until I got to the electrical. I
might have to order a tm1256 and see if I can see anything
different in it. Those electrical problems are aggravating things
to deal with.