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1953 GMC parasitic drain

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New User

Mar 31, 2018, 12:59 PM

Post #1 of 2 (482 views)
1953 GMC parasitic drain Sign In

My 1953 GMC truck has a short somewhere in the electrical. I have tried pulling fuses and nothing works. I’m using a 12 volt test light but none of the fuses seem to turn it off when pulled. I don’t want to take it to a mechanic because I think I will be able to do it myself, I just need some help.

Hammer Time
Ultimate Carjunky / Moderator
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Mar 31, 2018, 2:57 PM

Post #2 of 2 (460 views)
Re: 1953 GMC parasitic drain Sign In

You can't really use a test light any more as all cars have some degree of drain normally.

There is a procedure for finding a battery draw like that.

You will need a digital ammeter and a jumper wire with clips on the ends to do this.
First rig any door switches so you can have a door open without triggering the interior lights and unplug the hood light. Remove one battery cable and attach the meter in series between the battery cable and battery post. Take the jumper wire and also attach it the same way. Leave the jumper wire on for at least 30 to 40 minutes to expire all the automatic timers. Now remove the jumper wire and read the meter. Anything over 50ma is too much draw. The way you locate this is to start removing fuses one at a time until the meter drops to normal level. This will be the circuit with something staying on. Determine what components are part of that circuit and check them individually until the problem is isolated.

I admit you should have little or no timers on that vehicle. Don't forget to disconnect the generator/alternator and voltage regulator.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

(This post was edited by Hammer Time on Mar 31, 2018, 3:00 PM)

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