how to find a short - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**hilljob26** · 03-25-2008, 09:31 PM

my truck will drain the battery down after a couple of weeks of not starting it.there is great shop here in town that i can take it to but i would much rather try to find it myself,what do you guys do to look for this.im sure you will help many others out there as well as me

**DANTIP** · 03-25-2008, 10:01 PM

I would first leave the ground connection attached to the battery. Next put a digital multi-meter between the positive battery connection and the positive battery cable. Turn the meter to DC Amps and document the amount of draw you have (probably less than 1 amp). Next remove one fuse at a time and check the amp draw. When the amperage goes away, you have at least found the circuit with the problem. Next I would refer to a wiring diagram and check individual components in the circuit. You should be able to replace the defective component.

Good Luck!

**El Jay** · 03-26-2008, 12:55 AM

Quote:

Originally Posted by DANTIP

I would first leave the ground connection attached to the battery. Next put a digital multi-meter between the positive battery connection and the positive battery cable. Turn the meter to DC Amps and document the amount of draw you have (probably less than 1 amp). Next remove one fuse at a time and check the amp draw. When the amperage goes away, you have at least found the circuit with the problem. Next I would refer to a wiring diagram and check individual components in the circuit. You should be able to replace the defective component.

Good Luck!

I agree. That's the easiest, and simplest way to go.

Longhorn Man · 03-26-2008, 01:23 AM

I recomend doing the ground side of the battery. The draw will be the same, and the chance of a crash course in arc welding will be avoided.
If the reading stays steady through the test, and all fuses are removed, then go unplug the plug on the alt, then the voltage regulator (if it is still the old external set up) then back under the dash, the horn relay... I think that's it?

Now, BEFORE doing all this... was there anything you installed right before all this started? A stereo, or electric fan kit... or anything at all? Or did it just start happening all of a sudden?
Also... you are sure the battery isn't just a weak battery? you tried disconnecting it and hooking it back up after a couple weeks, and it fired right up?

haysonj · 03-26-2008, 02:58 AM

I just went through this on the electrical board. I used my multi meter on the battery ground like Longhorn said. My problem ending up being the pink tach wire was not on a switched source in the fuse panel and the battery drained through the MSD box. Took a long time to find it just by eliminating circuits Good luck on the hunt.

cranman · 03-26-2008, 03:12 AM

I agree to go on the ground side, that was how I was taught. Good luck, electrical t/s can be frustrating but look at the good side, the truck doesn't have that many circuits compared to new cars

DavesRide · 03-26-2008, 03:51 AM

I agree on the groung side also. While removing fuses make sure you don't turn on any power consuming items or you will have to replace the fuse in your meter. My truck just did this the other day and I unplugged my blower relay and the battery hasn't gone down since. Be sure to unplug it as well as the fuses while checking. One more strange tip. Look around when it is dark and look for a small light on somewhere ie glovebox. Just a thought.

1fun71 · 03-26-2008, 04:40 AM

Well Mike sounds like your truck is screwed so I guess I will have to take it off your hands I will come pick it up on friday

Longhorn Man · 03-26-2008, 05:20 AM

if your dome light turns on when you open the door... remove the bulb before starting

**DANTIP** · 03-26-2008, 06:44 AM

Glad to hear you found the culprit!

FYI, there is no difference between the meter being on the positive or negative side of the battery. The circuit may be made or broken at any point in the circuit with the same result because the current draw is identical throughout the circuit. It was also mentioned that the draw took several days to drain the battery, therefore the current draw through the drain had to be pretty low (below the fuse in the multi-meter).

Removing the interior light bulb was a good suggestion I had not considered.

Good Work!

Longhorn Man · 03-26-2008, 06:53 AM

he found the problem?
He hasn't even posted since he started the thread.

It is 10 times safer to remove the ground cable... doing it on the positive side is asking for trouble.
Otherwise, from an amp point of view, you are right.

03-25-2008, 09:31 PM	#1
hilljob26 Registered User Join Date: Dec 2004 Location: Gypsum Kansas 67448 Posts: 1,681	how to find a short my truck will drain the battery down after a couple of weeks of not starting it.there is great shop here in town that i can take it to but i would much rather try to find it myself,what do you guys do to look for this.im sure you will help many others out there as well as me __________________ 21 2500hd duramax 58 apache HILLJOB GRAPHIX--for all your graphic needs My build thread http://67-72chevytrucks.com/vboard/s...d.php?t=542497 LS ENGINE SWAP INFORMATION THREAD http://67-72chevytrucks.com/vboard/s...d.php?t=377348 4l60 to an NP205 http://67-72chevytrucks.com/vboard/s...43#post3697343

03-25-2008, 10:01 PM	#2
DANTIP Registered User Join Date: Sep 2001 Location: Fort Wayne, Indiana, USA Posts: 1,888	Re: how to find a short I would first leave the ground connection attached to the battery. Next put a digital multi-meter between the positive battery connection and the positive battery cable. Turn the meter to DC Amps and document the amount of draw you have (probably less than 1 amp). Next remove one fuse at a time and check the amp draw. When the amperage goes away, you have at least found the circuit with the problem. Next I would refer to a wiring diagram and check individual components in the circuit. You should be able to replace the defective component. Good Luck!

03-26-2008, 01:23 AM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: how to find a short I recomend doing the ground side of the battery. The draw will be the same, and the chance of a crash course in arc welding will be avoided. If the reading stays steady through the test, and all fuses are removed, then go unplug the plug on the alt, then the voltage regulator (if it is still the old external set up) then back under the dash, the horn relay... I think that's it? Now, BEFORE doing all this... was there anything you installed right before all this started? A stereo, or electric fan kit... or anything at all? Or did it just start happening all of a sudden? Also... you are sure the battery isn't just a weak battery? you tried disconnecting it and hooking it back up after a couple weeks, and it fired right up?

03-26-2008, 02:58 AM	#5
haysonj Registered User Join Date: Dec 2007 Location: Santa Maria, Ca. Posts: 1,423	Re: how to find a short I just went through this on the electrical board. I used my multi meter on the battery ground like Longhorn said. My problem ending up being the pink tach wire was not on a switched source in the fuse panel and the battery drained through the MSD box. Took a long time to find it just by eliminating circuits Good luck on the hunt. __________________ 69 Chevy 4x4 383 Power

03-26-2008, 03:12 AM	#6
cranman Registered User Join Date: Mar 2008 Location: Sanford NC Posts: 17	Re: how to find a short I agree to go on the ground side, that was how I was taught. Good luck, electrical t/s can be frustrating but look at the good side, the truck doesn't have that many circuits compared to new cars

03-26-2008, 03:51 AM	#7
DavesRide Registered User Join Date: Oct 2007 Location: Garageless, Missouri Posts: 408	Re: how to find a short I agree on the groung side also. While removing fuses make sure you don't turn on any power consuming items or you will have to replace the fuse in your meter. My truck just did this the other day and I unplugged my blower relay and the battery hasn't gone down since. Be sure to unplug it as well as the fuses while checking. One more strange tip. Look around when it is dark and look for a small light on somewhere ie glovebox. Just a thought. __________________ R.I.P ESLL Even as the body dies the spirit lives on in the people you touched

03-26-2008, 04:40 AM	#8
1fun71 Registered User Join Date: Jan 2007 Location: Kansas Posts: 119	Re: how to find a short Well Mike sounds like your truck is screwed so I guess I will have to take it off your hands I will come pick it up on friday __________________

03-26-2008, 05:20 AM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: how to find a short if your dome light turns on when you open the door... remove the bulb before starting

03-26-2008, 06:44 AM	#10
DANTIP Registered User Join Date: Sep 2001 Location: Fort Wayne, Indiana, USA Posts: 1,888	Re: how to find a short Glad to hear you found the culprit! FYI, there is no difference between the meter being on the positive or negative side of the battery. The circuit may be made or broken at any point in the circuit with the same result because the current draw is identical throughout the circuit. It was also mentioned that the draw took several days to drain the battery, therefore the current draw through the drain had to be pretty low (below the fuse in the multi-meter). Removing the interior light bulb was a good suggestion I had not considered. Good Work!

03-26-2008, 06:53 AM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: how to find a short he found the problem? He hasn't even posted since he started the thread. It is 10 times safer to remove the ground cable... doing it on the positive side is asking for trouble. Otherwise, from an amp point of view, you are right.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.