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One thing I found on my old truck that was draining the battery, was the On-Star even though it wasn't activated. I pulled that fuse and then it was all good, just a thought.
could you please tell me what fuse to pull mine is messing up too but there is no fuse labeled on star and thank you
 

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i just got back from getting a drainage issue fixed at a dealership,as it turns out,it was the gauge cluster module that was causing the drain,it was a spendy fix,but at least i wont have buy batterys for for a hundred a clip anymore
romymouse2000GMC My 2000 Sierra has a parasitic drain that can be stopped by pulling the instrument cluster fuse. Local cluster expert says that the diode problem is rare or non-existent on a 2000 model. But common with 2003+

Pulling the 5 amp fuse labeled " Audio system, Instrument Cluster, Climate Control System" solves the problem temporarily but I'm looking for a permanent fix. Any pointers would be appreciated. Romy
 

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the RAP relay in the bcm could be the problem. ign key turned off then 20sec the RAP relay turns off the power. the failure of the 20 sec shutdown will draw 250MA ...
replace the relay possible BCM.. being this old I had a relay intermittently fail to shut off the interior lamps..that was on a 1996 GM sedan...
 

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@j cat , not sure he has a RAP relay, the newer BCMs don't use one.
But, I think your on the right track!
@romymouse2000GMC stay in your truck after you turn off the key, leave the radio playing.
After 10 mins the radio should stop; at that time, try all of the other things impacted by the fuse you talked about. See what, if anything, is still working.
 

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battery drain update on 2000 GMC Sierra:
1. turned off key with radio on--opened door and radio went off
2. removed Prodigy tow/brake control
3. removed underhood light fixture (didn't work but bulb was good)
4. hooked up digital voltmeter and read 660 m amps
5. removed 15 amp fuse that controls the radio, climate control, and instrument cluster
6. voltmeter now reads 70 m amps
7. put everything back together and sat in truck waiting for the radio to shut off per previous posts;
8. radio did not shut off even after 15+ minutes; i think the retained accessory power relay is supposed to shut off after 10 minutes;
I'm going to replace the RAP#1 relay and see what happens next.
Any comments would be appreciated.
 

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Relay replaced and did the radio check again. Radio shut off at exactly 20 minutes after turning off the key. The new relay did not feel near as warm as the old one.
I'll have to re-run the meter check on Monday to see if the current drain changed.
and then disconnect the radio to make sure the only thing in the circuit is the instrument cluster;
too bad GMC didn't put in separate fuses for those items;
 

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Hello All,
So has anyone had any luck in figuring out what is causing the battery drain issue son our trucks?
I've googled the issue until my fingers have bleed and still have not found an answer. In the mean time I will continue to troubleshoot and take readings.
My husband had a battery drain problem with his Monte Carlo. They had to remove the Onstar unit. Good as new. Hope this helps
 

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2002 gmc sierra 1500 4.8
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If you have a battery drain it's easy to find with a DVOM meter. First step is to verify the drain. You should have no more than 300 Miliamp draw with the system powered down. Remove the negative battery cable from the battery and attach a jumper from the negative battery post to the positive lead of the DVOM meter set to Amps. Next attach a jumper from the negative meter lead to the battery cable. <Note that most DVOM meters have a built in 10 Amp Fuse. If you have a big drain you will blow the meter fuse so be careful and if you suspect a large draw an Amp Clamp is a better choice because it won't blow the meter fuse.
Now with the amp meter in place do not turn the key on. Remember the dome light will illuminate and draw amperage if you open the door. Another suspect is the glove box light. Very common battery draw that fools a lot of techs.<G>
Next start removing fuses one at a time until you find the circuit with the parasitic draw. Once you isolate the circuit it's just a matter of checking the accessories on that circuit.
Ok i have a rookie question do you pull the fuse and leave it out or do you pull it and if that wasn't the draw do you put it back and move to the next fuse ?
 

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Put it back and move to the next one.
 

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Give us some vehicle info and a problem description and perhaps we can help.

BTW, welcome to the site.
 

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2002 gmc sierra 1500 4.8
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I have a 2002 sierra 4.8 about 2 weeks ago i was on the fwy and i noticed my truck loosing power so i pull off and its dead so i assumed it was the alternator. so i bought a new one. I put it in and everything seemed fine drove a few blocks and the volt gauge started to drop and the battery light came on so i replaced the battery but got the same results. replaced the starter and the belt still nothing changed. It doesnt do it right away everytime i turn the truck off and wait a few mins it works a little while then drops
 

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Ok, that doesn't indicate a faulty circuit draw.

Before spending money on items like alternators and batteries, have them tested, your pocket will thank you

When you try to start the truck after it sits for awhile, does the truck start?

I suspect, a bad battery cable, or a dirty connection at a battery cable.
 

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2002 gmc sierra 1500 4.8
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it was late and the machine was down at autozone so i went ahead and bought the alternator. the battery, i could have used it anyway.. the starter had a bad wire so i replaced that ive already cleaned and inspected the battery cables and cleaned all the other grounds that go to the block and the body i also tested the fusible link to the alternator
 

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did you buy a new alternator or a rebuilt alternator ?
The plug in the back of the alternator check for any corrosion... its a field wire to control the alternator power output.
I do not like rebuilt alternators poor work armature and field coils are damaged over time ..
 
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