Odd Resistor Electrical behaviour

Posted by Dave Craft on January 19, 2004 at 19:11:26 from (24.27.10.239):

I've been tracing an electrical problem in my farmall 404 and finally arrived at the resistor as my problem. The tractor would attempt to start but when I let off the starter button it would not run. I subsequently determined that the push button starter is wired in such a way that it bypasses the resistor (hence the "almost" running). Once you let off the starter switch the electrical supply to the coil flows thru the other path which includes the resistor.

My problem: Once I place a wire between the poles of the resistor (essentially bypassing it) the tractor will run. At that point I thought....bad resistor! However I took it off and checked it with a voltmeter. It shows 0 ohms resistance between the poles (like a straight wire!). In addition when I test it in series with a 12 volt battery, the voltmeter shows 12 volts (essentially it is performing no resistance...again just like a straight wire). I would have expected the volts to drop across the resistor to something like 6 or 7 volts. I think normal running of the tractor requires something less than the full 12 volts, hence the need for the resistor.

So if it performs like a straight wire in tests it should allow the tractor to run...but it doesn't. Note that I think if I did straight wire it...or just use this "odd" resistor...I'd eventually burn the points, as 12 volts is too much.

The IH mechanic claimed the resistor had to be put on in a certain direction. That was wrong because A) the posts would have been labelled as such and B) I checked it in series with the battery with the current flowing to either post and get the same result.

Ideas? Is this resistor kaput? Could I have done something to cause it to die? I have noticed it being warm to the touch.

Follow Ups:

• Re: Odd Resistor Electrical behaviour Dale M 20:22:22 03/02/04 (0)
• Re: Odd Resistor Electrical behaviour Dave Craft 07:55:36 01/21/04 (0)
• Re: Odd Resistor Electrical behaviour Hugh MacKay 06:09:32 01/20/04 (1)
  • Re: Re: Odd Resistor Electrical behaviour Doug in OR 11:17:38 01/20/04 (0)
• Re: Odd Resistor Electrical behaviour Larry 03:11:36 01/20/04 (0)
• Re: Odd Resistor Electrical behaviour old 20:27:31 01/19/04 (0)
• Re: Odd Resistor Electrical behaviour RB 19:51:25 01/19/04 (0)
• Re: Odd Resistor Electrical behaviour JB 19:48:05 01/19/04 (1)
  • Re: Re: Odd Resistor Electrical behaviour John In Iowa 04:26:16 01/20/04 (0)

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