Author Topic: Dead Short with IGN off  (Read 126 times)

Offline 80HD

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Dead Short with IGN off
« on: December 06, 2018, 12:50:51 AM »
Hi All,
79  GMC C1500, twin tanks, BBC, A/C, Rebuilt motor w/700R4. 
With Ign off, every fuse and lead pulled from the fuse box under the driver's side of the dash, I have a pulsating current with a test light between neg batt cable and neg batt post.  Any thoughts would be appreciated.  Pulled the alternator plug and the A/C clutch plug, still pulsating test light.  This short will run the battery down in two days. The 700R4 has lead connected to power. If the lockup wire was hot with the key off, could it pulsate?
I can't think of anything that pulsates. Electrical crap makes my butt chew gum!
Thanks in advance,
Kim
Kim Burke

Online MIKE S

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Re: Dead Short with IGN off
« Reply #1 on: December 06, 2018, 10:12:38 AM »
You need to pull the main charge wire off the back of the alternator to eliminate that as a cause.

Offline 80HD

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Re: Dead Short with IGN off
« Reply #2 on: December 06, 2018, 10:24:19 AM »
Thanks for responding, I disconnected the alt completely.  Light is still flashing, no brighter, no dimmer.
Kim Burke

Offline 80HD

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Re: Dead Short with IGN off
« Reply #3 on: December 06, 2018, 10:25:51 AM »
Kim Burke

Online MIKE S

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Re: Dead Short with IGN off
« Reply #4 on: December 06, 2018, 12:29:50 PM »
Try disconnecting the plug on the driver side of transmission and see if that's it.

Offline 80HD

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Re: Dead Short with IGN off
« Reply #5 on: December 06, 2018, 01:36:07 PM »
I sure wanted you to be right but no dice. I'm starting to think it's related to the starter.  The starter is the only thing directly connected to the battery. Am I missing something else connected full time hot to the battery?  Can a solenoid do this?   
« Last Edit: December 06, 2018, 02:21:23 PM by 80HD »
Kim Burke

Offline Irish_Alley

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Re: Dead Short with IGN off
« Reply #6 on: December 06, 2018, 03:16:06 PM »
you could remove the power wire going from the starter to the cab leaving only the main wire going from the starter to the B+ and see what that does. if it still pulsates it would have to be in the starter, but i dont really see what in the starter would do this. but again i dont really see what at all in out trucks would do this. did you put a multimeter on the battery just to see what the volts drop to or even if you can see it?
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline 80HD

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Re: Dead Short with IGN off
« Reply #7 on: December 06, 2018, 04:39:52 PM »
Hi Irish,
I did put a DMM on the batt to determine the voltage(drop or pulse) and the voltage hasn't dropped but a .1-.2 of a volt the 2-3 hrs. I was farting with it.  The batt is 4 mos. old. BTW

I'm not sure I'm good enough to get a wire off the starter without removing it.  That will be another day.

The truck is going into the tranny shop tomorrow. The 700R4 is due for a much needed overhaul and buildup. The motor can power through 3rd gear at will!

Thank you all for the responses, I'll get back on it when it returns home.
Kim Burke

Online bd

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Re: Dead Short with IGN off
« Reply #8 on: December 06, 2018, 07:43:33 PM »
The link to YouTube is unavailable for viewing.
Rich
It's difficult to know just how much you don't know, until you know it....
In other words... if people learn by making mistakes, by now I should know just about everything!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Online MIKE S

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Re: Dead Short with IGN off
« Reply #9 on: December 06, 2018, 09:51:11 PM »
Aftermarket sound system? Alarm? Anything under dash that has tapped into a wire. Headlight switch should be live even with fuses pulled. It has a built in circuit breaker. High speed A/C relay doesnít have a fuse in fuse box. I think horn relay is also powered. Pull connectors to these one at a time.