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Discussion Starter #1
Hello. As the title states, my 2001 S10 with a 4.3 has developed heavy parasitic drain. It's enough to kill the battery if I leave the truck parked a couple of days. The alternator and the battery are both new, and had been working fine up until a couple of months ago. I put a voltmeter on it and pulled every single fuse looking for that amp draw, but nothing made a difference. So I'm at a loss. What are some things that are electrical and could stay on mistakenly, that aren't tied to the fuse panels?

Around the same time this issue appeared, my radio stopped turning off when I open the door with key removed from the ignition. It stays on for longer than the usual ten minutes as well. It would stay on all day if I didn't power the head unit off. I've also noticed the security light appears to be flashing. Another strange thing that happens occasionally is an alarm will go off. I have no idea what triggers it, and actually I didn't even know this thing had an alarm. But sure enough, it will beep and beep until I start the truck again. This has only happened a couple of times, but I've begun to wonder if it and the radio thing aren't part of the issue.

Any advice on what I can do to stop this and get my truck back to normal would be appreciated.
 

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may be that you bcm isnt going into sleep mode
normal cause is a domelight problem,aftermarket radio install that went bad etc.
You can try unplugging the BCM and see if battery stays charged.
Even new alternators have been known to drain a battery if they have an internal problem,may want to try disconnecting that too.
Only do one thing at a time so you can eliminate and move on to the next.
how much is your draw?
 

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Discussion Starter #3
may be that you bcm isnt going into sleep mode
normal cause is a domelight problem,aftermarket radio install that went bad etc.
You can try unplugging the BCM and see if battery stays charged.
Even new alternators have been known to drain a battery if they have an internal problem,may want to try disconnecting that too.
Only do one thing at a time so you can eliminate and move on to the next.
how much is your draw?
Seems to be a fairly constant 20 mAmps or so. Or I might have read the meter wrong. With the dial at 0/200 setting on my multi, it read -0.2 spiking to -0.3 occasionally. This BCM might have gone bad before I bought the truck. I just remembered that the door buzzer was constantly on when I opened the driver door, even with the key out. It was so annoying that I eventually pulled the BCM and popped the dumb little piezo buzzer or whatever it is off the module. No more door chime. Is it possible the chime circuit is still getting power? Or is it possible the chime is triggered by another circuit that is stuck open, and the always on buzzer was merely a symptom of that?

Also, and this would be great to know before I go pulling one of these at the junkyard, are the modules swappable from Blazer to S10, and across the entire Gen2 vintage, or are there specific years I need to look for? Seems like my local yard only has Blazers these days.
 

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20ma isnt the cause of a dead battery in 2 days
you need to fix the door switch problem,pulling the speaker doesnt do anything for the circuit,its on the output side of it.
You need to fix the input side of it.
Unless you really know what youre doing I say no to swapping BCMs
fix the problems with yours first
I dont think your BCM is bad,just confused because the door switch is always on.
 

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Discussion Starter #5
20ma isnt the cause of a dead battery in 2 days
you need to fix the door switch problem,pulling the speaker doesnt do anything for the circuit,its on the output side of it.
You need to fix the input side of it.
Unless you really know what youre doing I say no to swapping BCMs
fix the problems with yours first
I dont think your BCM is bad,just confused because the door switch is always on.
When you say the switch, do you mean the little plunger the door contacts when it closes? I've had to replace that part already when the original one got crushed somehow. Maybe I got a bad replacement. It would be a pretty cheap fix if that was what is wrong with it. Is there any way to verify for sure which BCM input is reading as always on? I assume I'd need a wire probe for my multi if I wanted to start checking those lines.
 

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look thru the stickies and find your wiring diagram
trace out every part of the BCMs logic related to security and domelight.
Im betting the trigger is somewhere in that
 

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switch may be good- wires might be bad
 

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I agree.That switch is simply a ground. If the wire to it got damaged when the old switch got crushed it could be shorting to ground.
 

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Pull the negative off the battery. Put the test light between the post and the ground wire. If the light illuminates, you have a draw. Use the fuse pull method to find the draw; when the light goes out, you found it.
 

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Since he states "Seems to be a fairly constant 20 mAmps or so", I think he's past that point in diagnostics. Will 20 mA light a bulb?
 

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I have a 1995 s-10 that had the same issue.

Theres a small draw in the milliamp range to power smog timers and other electronics. Thats normal.

The parasitic draw on my S-10 was the factory installed radio. Has 2 fuses one for the clock and station memory the other for when the radio is on.

Something in the radios circuit that keeps the radio's station memory and keeps the clocks time went bad and was causing a 2 amp drain. That's enough to kill the battery in 2 days.

The temp fix was to remove the fuse that powers the clock and radios memory circuit on my truck.

You need to go back and check every fuse again with an ammeter til you find the circuit.

It may take a some time for the parasitic drain to start after you reconnect the battery as all the circuits reset after the power loss from disconnecting the battery. So the drain might not show up right away after reconnecting the battery.
 

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Discussion Starter #12
Thanks so much for the help everyone. I've got a new switch but maybe I should go look for a wire too. I'll also check on my aftermarket radio. It's a cheap piece of crap so it might have gone bad.
 

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Thanks so much for the help everyone. I've got a new switch but maybe I should go look for a wire too. I'll also check on my aftermarket radio. It's a cheap piece of crap so it might have gone bad.
Just pull the plug out of the back of the POS radio and see if your problem goes away. A lot of aftermarket radios aren't installed correctly using Metra connectors. Just wires cobbled together which can cause multiple issues including current draw when off.
 

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Just pull the plug out of the back of the POS radio and see if your problem goes away. A lot of aftermarket radios aren't installed correctly using Metra connectors. Just wires cobbled together which can cause multiple issues including current draw when off.
If its 20mA thats normal after the BCM and security system goes to sleep
Newer models with on* and other crap(my Escalade draws 15mA just for the trailer brake) its normal up to 50mA.
Neither of those figures will drain a good battery in 2 days.I have several that sit for 3 months or more and fire right up.
Not saying thats a good thing to leave a battery that long tho.
 

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Discussion Starter #18
After this weekend's testing I think I can rule out the radio being bad. I unplugged its fuses and left it overnight, and the battery was still charged down to about 68% in the morning. I've swapped the door switch but haven't found wiring to replace the existing yet. We'll see what that does.
 
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