S10 battery drain

My understanding is TBC is truck body controller. You may need to unhook any added on items to see if that clears the issue. radio if its not stock, those door locks etc. Not sure if you have wet shorted tail light or wrong bulb in socket etc., probabaly not that anyway.

my .02

Thanks guys. Brake lights work just the uppur one on the cab doesn't work. I unhooked the alternator - no drop. Pulled the relays (? little boxes in the fusebox on left fender)- no drop. Pulled fuses - one marked int batt dropped from .650 to .100 amps. What does Int Batt mean? TCB fuse also causes drop. Will try to disconnect doorlocks tomorrow.

To check amp draw you need to check it with the battery hooked up. Just checking between the cables you will get a false reading. To many computers and other stuff that has to power up when the battery is first connected. Hook up the battery and give everything time to power up and then power down to get true amp draw. Like 10 minutes or more. And like said start unplugging till you find it. Good luck MT

Thanks MT2500 How do you check battery draw with the cables hooked up? I have a radio shack multimeter with 2 probes. The only way I know of is to remove the ground cable from batt and check between. You said hook everything up for 10 minutes then check everything. Do I need a different tester to do this?

If you're using an ammeter function, the meter has to be in series with the cable and the battery. (Yes, a clampon might work)

But you have to let the current flow long enough for all the systems to go stable. Every time you break the connection to the battery, you may activate some systems and the initial readings will be too high. They will stabilize (or not) if you just wait.

Usually it just takes a few seconds to drop into sleep mode and you can watch it on the meter. I have heard some cars can take as long as 10", but I never run into them. The poster would benefit by setting his meter up with alligator clips on the ends so that passers by don't think his hands are glued to the battery.

and whatever you do...with the meter in the line..DONT CRANK THE ENGINE. The meter will blow an internal fuse which is repairable, but your test will be abruptly over until you fix your meter.

also..don't think a battery which is 1 year old cannot still be faulty. You might be looking at other casues if your battery drain test checks out.

A volt/ohm meter with a clamp on amp probe works a lot better. That way you can leave the battery hooked up direct. You may be able do it with your tester if it will carry the amps hooked in series and gives you a good accurate reading. But remember some raido shack ohm meters run threw resisters that pull some current and may throw your reading off some. Some cars take longer than others for everything to power down. Hook it up and watch for your volt meter. Good luck MT

It was the battery. I charged it up out of the vehicle and cept checking it with a voltmeter and the voltage kept dropping slowly but steady. Then I took it to a napa store to have it tested and they said it was no good. The first time I had it tested was at a tractor supply store. They said it tested fine. Some of these store clerks don't have the training to do a proper test. Anyway thanks for all the help.

Thanks for posting back on how it went. Glad you found it. MT