1996 ford 3930 key switch wiring

[baronthered]

well my nephew made my day today one of those I wish I had stayed in bed. To cut a long story short the pto engagement arm was just enough off the safety switch that it didn't start, no problem happens occasionally. My nephew was going to move the tractor and it wouldn't start me being on the other end of the farm he didn't want to give a yell on the cb or bother to see what I had to say about it. He unhooked the wires from the back of the switch :smiley_aafz: :mur: and the only one I can figure out is a brown wire and that's only because the terminal for it is larger. anybody have a picture or diagram of what goes where on the switch? I have a wiring diagram of the electrical system but nothing on the switch or the diagram tells me what goes where. If needed I do have some pics of the switch but my nephew handles that kind of thing for me and after the chewing he got I don't think he'll be back for a month or two.

 

[CharlieS]

I dont have a switch diagram, but it should be fairly simple to test out with an ohm/volt meter. On the switch itself the larger terminal you mention should be the battery connection, and the larger brown wire you mention should be direct power to the battery.
With power hooked up to the switch (note be careful not to short anything hot to ground) ground one lead of a voltmeter and test each terminal. one terminal will be powered when the key is in the on position, (usually the first terminal to the right of the battery connection) one terminal will have power only when the key is in the start position (usually the second terminal to the right) NOTE these positions will be with the key slot facing you. Then color match/trace the wires back to the source. Starter wire will hook to the momentary contact and runs to the starter solonoid, and connects to the starting (momentary) position on the switch, fuel pump will hook to the run position, or constant powered terminal when key is on.
There should also be a wire or two feeding power to the instruments that will connect to the constant power on terminal of the switch.
You may need to use a jumper wire from the battery to test each wire. With the tractor out of gear, park brake set, jump power to each wire. Starter of course will attempt to start the engine. for the fuel pump actuation you should hear the pump solonoid click. remaining wires should be instruments etc requiring constant power when the key is on.

On a side note, for future reference, if you look at how the micro safety switch is mounted under the pto actuation lever, a couple of small screws hold it in place and these can work loose allowing the switch to get out of adjustment. At least i've had that happen once or twice on my 3430. The first time it was a bugger to find.

Hope this helps.

 

[baronthered]

Charlie thanks for the help. I'll definitely give her a whirl soon as I can get my hands on a volt/ohmeter sadly mine took a dump on my about a month ago. That's the way it goes I guess don't need something everythings fine need something and it's either missing or broke. Luckily I have a neighbor who was an electrician and has a good setup.

 

[baronthered]

Well my buddy doesn't have a voltmeter right now loaned it to his FIL and it never came back. I have all the wires traced out just need a pic or something to tell me which wire goes where. I also tried rigging up a little test light but that didn't work so hot for me either.

 

[Soundguy]

Charlie thanks for the help. I'll definitely give her a whirl soon as I can get my hands on a volt/ohmeter sadly mine took a dump on my about a month ago. That's the way it goes I guess don't need something everythings fine need something and it's either missing or broke. Luckily I have a neighbor who was an electrician and has a good setup.

test lamp will work just fine..

soundguy

 

[baronthered]

Here's a little pic of what I have. Still Can't get the bleeding thing to crank though. guy at the shop told me how everything goes back in but still no bones. I'm hoping my nephew didn't let the magic smoke out of something on me. :confused2: The jumper is something my father in law did when he was still alive and I'm not sure where it goes for sure I think it goes to the solenoid but am not sure which wire it is supposed to sit with if it does.

 

[CharlieS]

Look on the bottom of the fuel pump (right side of the tractor facing forward) there is a wire attached which should match one of the wires at the switch. I suspect this will be the brown/red striped wire, as on my 3430 its a faded pinkish color/brown stripe. The terminal connection on the switch shown in your diagram for this wire attachment, should have constant power with the switch in the on position. This leaves the remaining wire which should then run to the starter solonoid and connect to the momentary contact, (start position) of the ignition switch.
The red wire you mention concerns me since you indicate it was added. This makes me suspect a broken wire between the switch and connected load. (starter solonoid?)

You mention 2 large wires, brown and white connected to the switch, are they both the same size or is one larger than the other? If different sizes then probably the larger of the two will be direct power from battery to switch, and the other carries power to the various instruments. In either case you need to establish which wire is hot, and supplies power to the switch.

At this point you need to, as mentioned above:
1- find which wire supplies constant battery power to the switch.
2- establish for sure which terminal on the switch does what, finding the key on constant powered terminal and momentary on start position.
3- trace the color coded wires to they're respective terminations and find out what the red jumper wire you mention does, where it terminates at.

A test light, and/or ohm/volt meter is going to be needed to reliably check these functions.
keep notes, and draw diagrams if needed and as you sort out each wire connect it to the proper location on the switch.

 

[RickB]

Relative to the non-stock red wire, the most common reason for added wiring on these tractors is to bypass the neutral saftey switch. The red wire probably runs from the key switch to the starter solenoid coil. Accordingly, make sure the both speed and range shifters are in neutral while you are playing with the wiring on this tractor.

 

[baronthered]

Thanks for taking the time to help gents. I'm good at tearing an engine down and can wire a house or factory and at one time was a lineman ( some irony there huh? ) but for some reason the electrical system on this thing (and cars and trucks) seems backwards to me.

The large brown wire is much bigger than the others and has a larger terminal end on it that matches the big terminal on the switch. the large white wire has the same size terminal as the others but the wire is larger than all of them except the brown one. The guys at the shop said the brown/red striped wire is for the "heat" (glow plugs) and the white/yellow dotted wire is for the safety switches. I have forgotten what he said the white wire is for (don't have the hand drawn diagram he gave me. not a good one at that).

On a slight side note, the guy at the shop didn't really have anything except the same wiring diagram I have I just hope he's right. I hooked all the terminals up like he said and I have the idiot lights come on when I hooked everything up like but still no cranking.

My nephew mentioned when he was going to start it the other day he forgot to take it out of gear and it cranked about half a revolution then stopped.

What are the odds my solenoid is shot?

The added red wire I do believe is going to the solenoid I still have to track the little bugger down all the way but it is in that direction.



Ugh the more I think about this the more I think I'm going to have to really tear into the old girl.

thanks again gang. You are keeping me sane in this hot weather.

 

[baronthered]

Just an update. Tracked all the wiring down and confirmed their locations and termination points. Got the new voltmeter out and checked all the locations on the switch and marked them hooked them up and still nothing. Anyone know of some test I can do on my solenoid? any other thoughts are appreciated as well.