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Short to battery?

so here’s the deal, i bought a 2000 chevy impala 3.4L used. It worked great for two days, then the battery started going dead, it had a rough idle and the check engine was on. I changed a shorted o2 sensor. the car Runs fine now, but the battery is still dying and now having a little trouble starting. brand new battery, plugs and wires, starter, alternator. The thing is, the radio was stolen just before I got it ( i got a great deal) and it seems to have messed up the ignition switch when they ripped it out. sometimes power or even head lights will go on or stay on when I take the key out. I have been fixing this by jiggling the key in the tumbler until they turn off. I can’t find any shorts in the system, but it seems that something is grounding or shorting and causing the battery to die. I can’t afford to take it to a mechanic right now, but have all the tools and usually do all my car stuff myself anyway. ANY GUESSES?

It’s not a matter of guessing. It takes patient, dedicated troubleshooting to locate the source of your problems. First, find a wiring diagram for your Impala.

Turn off all of your accessories and disconnect one lead to the battery. Hook up an ammeter there. Then pull fuses, one at a time, until your meter shows a current drop. Then replace the fuse and separate each electrical connector in this particular circuit until you find the source of trouble. I should add that you have more than one fuse box.

Sounds like an issue with the ignition switch.

The radio was stolen. Did you or anyone replace the radio? If so, did you put in a stock radio or aftermarket?

@ Keith I didn’t replace the radio yet. I know that it has a constant current that i’ve already taped up, so it’s not that. FordMan59, I’m going to replace the switch either way, but am worried that it’s not in the actual switch. Have you heard of this before? why do you think it’s in the switch?
SteveF: thanks, for the advice, i’ve got a multimeter and a test light, don’t have an ammeter, could i just use the multimeter?

There could be more than one “hot” wire to your radio. Also, was teh radio that was stolen the factory radio or an aftermarket upgrade?

Blaineyb, a multimeter IS an ammeter, plus it has other useful functions as well. That is exactly what you need.

thanks guys, I’ll give it a shot with the ammeter. as you can tell, i suck at electrics. Keith, I don’t know if it was an aftermarket or not. it was already gone when i got the car. the diagram for the radio has two hot wires, one which is always on and another (which i checked and seemed fine) which should only get power when the ignition is turned on. this is driving me nuts guys, thanks again.

one more thing, i’ve got settings for both ac and dc. which would i be using? i would guess dc.

It’s dc. And if you test voltages, use the range that includes 12 volts. But you are testing current (amps) so you would not be concerned with voltage ranges.

I don’t know which multimeter you have or what its choices are. If it has a socket for 10a, plug the red test lead into that one to begin. This lead touches the positive (+) battery post.

It would help to have an assistant. One person keeps the leads in place and reports meter readings while the other removes and replaces fuses one at a time.

The constant power going to the radio is for the memory inside it to keep it alive.

If jiggling the ignition switch clears the problem with the accessories staying on then you need to work on the adjustment for the switch. The contacts aren’t in the correct position and are making contact when they shouldn’t be.

Make sure your meter has at least a 1 amp scale. The 10 amp scale (move the test lead) is better. 100ma may not be enough and you will pin the meter or damage it…

After you find the parasitic load, and fix the problem, the parasitic load on the battery should be less than 150ma. Even that is a little high…Make sure there are no lights on, (the one under the hood?) during the test/search…

so many people write in with problems and then you never get to hear the answer so…
there were two different problems happening at the same time, both (i think) because the radio was ripped out of the dash.
1: the harness for the ignition switch in the dash had all kinds of shorts. I was able to replace or fix all of them
2: the key cylinder wasn’t sitting correctly in the switch and pulling power even in the off position. unfortunately, i replaced the switch and cylinder. If i had looked at it myself instead of taking it to a mechanic, it could have been repaired and saved me a small boatload of money. lesson learned.
thanks for all of your help


almost forgot, i took off the hid conversion kit and reinstalled oem headlamps. i don’t think that it was part of the problem but always hated those things, not to mention they’re not street legal, and it was pulling extra load from the battery (while running) as well.