Ford 640 wire fire.

grandpa Love

Well-known Member
Working the 640 pretty good today. After an hour the alternator wire was smoking bad. I just added a wire to acc on switch , oddly that wire had been burnt at some point. After I added that wire alternator was charging. But it burnt the wire today. Took wire off. Still working. 3 hours later I accidentally flipped lights on. Every light wire was smoking with some flames! Crap!!!!! Took 2 seconds to realize what it was ,cut lights off. Worked 3 more hours off and on clearing brush and pushing up burn pile. Tractor runs fine. Except alternator ain't charging. Any ideas on what happened? Thanks Kevin in Central AL
 
Well, obviously there is a short in the light wiring circuit, sounds like more than one short if all the light wires were smoking.

The wire added to the acc, where does that go? To the lights?

The wire from the alternator that was smoking, that could have been caused by the excess load from the shorted light circuit, causing the alternator to work extra hard trying to keep up.

It could also be caused by a shorted alternator or battery connected backward. You may want to take the alternator in and have it checked.

Or it could be caused by the regulator failing to cut the voltage back, causing the alt to overcharge.

And, it could be the wire is too small for the alternator amperage. Typically, alternators use at least a #10 wire, higher amp alt needs larger, #8 or #6.

Looks like you need to do some clean up on the wiring. Check carefully, a smoking hot wire inside a harness can take the insulation off adjoining wires, causing other problems.

You missed a good chance for disaster! Be careful!
 
Lights have been wired up and working for a year. Head lights. And 1 on each fender. All wired to one switch. alternator wire to acc was not hooked up when I got tractor 18 months ago. 3 wire alt. Alt never charged. Did some research on here and added the wire and it charged correctly. We have used tractor for short periods of time for last few weeks. Today was longest continues run. Took over an hour for alternator wire to smoke. Then several hours later the lights smoked. Maybe alt wire needs resistor? Maybe when it melted it burnt insulation off light wires? Used tractor for couple more hours ,no problem. Hope it cranks in the am. It's 70 miles away at a customer 's house! I guess God wasn't busy enough today lol. I gave Him something else to do!
 
Well You have a short some where. Also what gauge of wire are you running from the alternator to the battery??? Alternators can easily put out much higher amperages than generators did on these old tractors. So you need at least a 10-12 gauge wire for the charge circuit.
 
Don't know a lot about Fords, so Tractordata says this tractor was originally a 6V, which I realize their info is not always the gospel. So if it was converted to 12v and alt. what brand alt is it and how many wires to it?
 

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