1990 k1500 draining batteries

[Delta9]

Not sure if anyone had the same issues as me, but the truck is turned off everything is off and it will drain a battery just sitting. Any suggestions? Please help!!
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[speedygonzales]

Thought I had the same issue. Turned out to be the battery.

With a DVM set to current (10amp) scale. Take a battery cable off at the battery and put one meter lead on the cable and the other lead on the battery terminal you just disconnected it from.

2 things to watch out for. One is the polarity of the cables. If you take off the negative terminal. The positive lead goes on the cable. If you take off the positive cables, the positive lead touches the battery.

The other thing to look for is a blown fuse in the meter. In the above case you are looking for 0 current. Or very close to 0. With a blown fuse, you will see 0 current every time.

I have yet to see a meter that does not have a blown fuse.

[jerrymp]

I had the same problem with my 98. Drained a brand new battery down to nothing over a period of 5 days. Funny thing was, it just started doing it one day. Out of the blue. Finally figured out it was something in the radio (don't know what) so I just pulled the fuse that keeps current to the radio even when the key is off. No more problem. Of course the radio does not keep the station pre-set buttons but I could care less. If you ever find out the problem, please post it here.

[Delta9]

Thanks guys i dont have a DVM but i did notice the wire harness that connects the the alternator is in real bad shape. As far as the radio thing thats also pretty possible, but i have a question about the radio as well. Its an aftermarket headunit and everything seems to b connected properly, but i get no sound but and audible beep when i push buttons or change the volume. Also i know what im doing with car audio but i just never seen this b4
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[OrangeAnimal]

Just another very quick and easy way to find out what's draining your battery.

1. Disconnect the negative lead.
2. Take a test light connect the alligator clip to the neg side of the battery. Take the probe end and stick it in the negative cable.
3. The light on the tester is now more than likely lit. If not then something is not draining the battery.
4. Start in the cab and pull each fuse one by one. When you get to one where the light goes out that's the circuit the draw is on.

Most likely the courtesy light fuse sometimes the switch inside the glove box breaks causing the light inside to stay on. Also when you do this if you have the door open or the hood light on or connected it will show like a draw. Generally I pull the fuse for the courtesy lights first and see if the bulb on the tester goes off. If not I know it's somewhere else.

I learned this trick many years ago from a very smart guy. This is the quickest way to go thru your circuits IMO.

[Mr_Rich]

One thing you might do if at all possible. Replace some of the courtesy light bulbs with LED's. I noticed that when I mistakenly left a light on all night that they draw so little amperage that I still had battery power left the next morning. Worth a shot...