Need help. Stumped.

[meck]

This morning, away from the house, my trusty 640, with 12v conversion, suddenly wouldn't start. Cranks, but sounds like no fire. I had a roll of wire with me, so I tried hot-wiring it from the B+ to the coil. It started immediately. Got it to the barn. Disconnected the jumper wire from battery to coil, checked volts from the ignition switch to the coil and got full battery voltage, but it would not start. Put the jumper back on, and it started instantly.

I tested the key switch multiple times with the multimeter, and it worked every time. The only other thing different is that the voltmeter on the tractor also stopped working, but it is not in the direct circuit from the key switch to the coil, and I don't see how it can be related.

I'm stumped. Will appreciate any help or advice that someone can give.

Thanks.

 

[TomIn]

I have a 640 that began quitting on me after 30 minutes or so. I suspected a bad coil, so bought a replacement. When I
tried to disconnect the wire from the old coil, it broke. I turns out that the stranded wire had frayed, corroded, or ??
inside the insulation. I put in a piece of new wire and my problem was solved. You might try just replacing the wire to
the coil (or disconnect the wire and put in a jumper.) You might also have some corrosion on a terminal somewhere. (the
jumper may just provide a better connection.)

 

[meck]

Thank you for your reply and helpful suggestion, but the problem has been worked out, and I am embarrassed that I didn't look into it deeper before asking for help. At the moment, though, I was totally stumped.

As I said when I wrote, I had checked the ignition switch, and it worked. But when I took another look, I discovered that before I got the tractor someone had totally rewired it in a way different from what I was expecting. The switch did test out okay, but the switch is only being used to control a relay. The person rewiring put in a 30 amp fuse connection, then a relay to handle all power. The relay, I discovered when testing, was erratic, so a replacement will take care of the problem. Until I can get to town to buy one, I'll just "hotwire" it to run. I still don't understand, though, why the voltmeter quit at the exact time and is totally nonfunctioning even when the relay decided to work. That's a mystery for another day.

Thanks again.

 

[Royse]

Why not remove the relay and wire as original?
The only benefit I see is if they ran the headlights off the relay too.

 

[meck]

Good idea, Royce. I'll do it. I have a universal ignition switch already that will save me the cost of a new relay. I don't know why the person wired it with the relay controlling power to the power distribution block because there is a second relay that controls all lighting. It just seems an unnecessary complication.