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Electronics => Beginners => Topic started by: darinsquared on November 19, 2016, 09:27:45 pm

Title: Finding DC shorts
Post by: darinsquared on November 19, 2016, 09:27:45 pm

I read a post/article on diagnosing short circuits.  I thought it might have been in this forum just recently (this week) but I cannot find the post.
 I am trying to find a short in a long wire run so a conductivity test will not work.  One method was using a infrared thermometer or camera.  I have access to a thermometer but I do not know how precise it is but I do not have a camera.  I thought there was another method but I cannot recall the methodology.  Any help would be appreciated.  I do not know if this matters but there are multiple wires in a plastic loom.  I assume the most likely spot will me a "joint" or where the wires bend.

Title: Re: Finding DC shorts
Post by: darinsquared on November 20, 2016, 01:27:46 pm

 Thanks for the reply. I do not have the equipment you mention, I am just a hobbyist interested in electronics.   the wiring issue is on large farm equipment.  Your second method may work however the wiring harness with the short is in a group of about 10 wires so there would be a lot of trial and error with that amount of combinations.

Title: Re: Finding DC shorts
Post by: 3roomlab on November 20, 2016, 01:39:33 pm

Quote from: darinsquared on November 20, 2016, 01:27:46 pm

Thanks for the reply. I do not have the equipment you mention, I am just a hobbyist interested in electronics.   the wiring issue is on large farm equipment.  Your second method may work however the wiring harness with the short is in a group of about 10 wires so there would be a lot of trial and error with that amount of combinations.

what test gear do you have or can have access to? DMM ? a neon lamp test stick? cable tracers?

Title: Re: Finding DC shorts
Post by: Fank1 on November 20, 2016, 02:45:46 pm

Put a resistor in line at the source, battery, to limit the current to an amp or two and then follow the wire using a compass.
The deflection will change when you pass the short.

Title: Re: Finding DC shorts
Post by: German_EE on November 20, 2016, 07:23:50 pm

Put a resistor in line at the source, battery, to limit the current to an amp or two and then follow the wire using a compass.
The deflection will change when you pass the short.

 :clap:  :clap:  :clap:

Somebody give this guy a prize, that's the most ingenious solution I have ever heard.

Title: Re: Finding DC shorts
Post by: mikeselectricstuff on November 20, 2016, 07:38:17 pm

Connect a low - impedance audible AC source ( e.g. audio amp speaker output) across the end of the cable.
This will create a current loop from the end of the cable to the short.
Then use a small handheld coil and audio amp to follow along the cable until the tome disappears, which will be near the short