Re: ground fault, what am I doing wrong?

Posted by John T on March 18, 2006 at 10:56:04 from (66.244.90.98):

In Reply to: ground fault, what am I doing wrong? posted by mikeinWA on March 18, 2006 at 09:21:29:

Mike, a couple disadvantages of a one wire alternator is they draw a slight current when not in use plus they require a certain RPM before they kick in and excite.

Heres how I use a simple test lamp to find major shorts, however, if the short is very minor and high impedance there may be insufficient current draw to lite the lamp, in which case a meter would be more accurate. The test lamp is the type with a wire and alligator clip on one end and a sharp needle probing tip at the lamp end.

Remove the hot ungrounded battery cable from the battery post,,,,,,,,attach the wire and alligator clamp end of the test lamp to the hot ungrounded battery post,,,,,,,,NOWWWWWWWW with the other sharp end of the lamp youre looking for a ground return path which (short to ground) will lite the lamp when you probe to it with that sharp probe end of the test lamp,,,,,,,,,,probe by touching the sharp end to various wiring and switch input terminals (such as the BAT input terminal on the switch) and when youre at a point that has a connection to ground which lites the lamp, you found a ground fault. If you find a point that lites the lamp that has more then one wire to it, disconnect the wires one at a time until you isolate which circuit has the path to ground. Locations such as tractor lights etc will make the lamp glow cuz that represents a circuit to frame gtound, however, if a switch is good and off and works, a probe to the BAT input side of a switch SHOULD NOT glow the lamp unless the switch is bad or has an internal short. Remember with this test the hot ungrounded battery cable has been removed but its ground cable is still connected to frame ground, therefore, there should be no voltage on any tractor wiring locations/terminals, its paths to frame ground youre probing for that cause the lamp to glow since one lead is on the hot ungrounded battery terminal and the other probe lead needs a frame ground return path to lite the lamp.

Clear as mud???????

John T

Replies:

• Re: ground fault, what am I doing wrong? Jon Hagen 11:59:48 03/18/06 (1)
  • Re: ground fault, what am I doing wrong? John T 13:20:45 03/18/06 (0)

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