Re Wiring main switch John Deere 820 (1973)

2345joes · Oct 9, 2021

Hey everyone,

First off the battery box and dash need some dusting.

I'm trying my hand at electrical. The original switch was jumped to a toggle instead of ignition by the previous owner. I have a wiring diagram and a new A&I main ignition switch. The back of the replacement has numbering that corresponds to the wiring diagram (sort of). Does anyone have experience with this type of switch (nesan)?
Below:
New main switch
Existing main switch
Wiring diagram

I can include more photos

Thanks in advance!

Joe

Zebrafive · Oct 10, 2021

Any reason you did not get JD P/N AL19890 main switch/key switch?

2345joes · Oct 10, 2021

I have not looked, but maybe worth a call.

Roadworthy · Oct 10, 2021

I'm sure your new switch CAN be wired in but would not trust that the numbering is the same as the diagram. I'd grab an ohmmeter and see which terminal connects to which in the various switch positions. From there I'd try to identify what's what between real world and your wiring diagram. One of your wires will be hot from the battery all the time. The others are circuits which it completes for the various switch positions. Be conservative on this one to avoid melting something down - likely only insulation on wires.

2345joes · Oct 19, 2021

Power is the middle terminal. I ordered the JD version with a key for around $70. I'll post a photo of it when I get it.

CoyPatton · Oct 20, 2021

It will take some doing with your new switch, but ohm out what each function does from the battery terminal.
I recently put in a new ignition switch on my yanmar. On mine I have 6 terminals. An Accessory terminal labeled ACC, 2 thermostart terminals (one with a left turn of the key and the second active in the start position), the starter terminal, a terminal to the fuse block, and last the battery terminal.
If you can ID each terminal, then run your wiring diagram to match the wires terminating point with the switch function.
None of it is hard work, but time consuming. Fortunately tractors of this era are electrically simple.
A multimeter can assist with IDing the wires either by finding voltage or ohming out.
Make plenty of notes about switch positions and label wires as you determine their usage.