I bought this car from my brother in law a couple of months ago. Unfortunately, I don't know much about working on cars, and I only have a limited selection of tools unless I drive over to his place. The problem right now is that the battery indicator is constantly on and all lights are dimmer than usual. This problem has happened a couple of times, for long periods of time, and then mysteriously went away again. Before it manifested itself in this way, occasionally when at high RPM, all of the electrical components would suddenly get more power than usual, e.g. the lights would get brighter and the air would blow harder, but only very briefly. That went away after I got the first persistent battery warning and checked the 6 month old battery to find that it had blown both of the vent caps clean off.

Previous to that, the only electrical problem we had was that it was blowing the ignition fuse, but we managed to find that the problem was a loose bracket on the starter was grounding out the system. Since we couldn't find the appropriate size fusible link, I replaced the ignition fuse with an 80 amp instead of the 50. I don't know if that might have something to do with it, but I doubt it.

Here's what I know:

- I have yet to kill the battery, thus I know that the alternator is working. I doubt that I could drive the car at highway speeds for more than a couple of minutes without it, but I've driven it about 50 miles with the light on and the condition hasn't significantly changed.

- Two weeks ago, after I replaced the battery, I took it by a parts store and had the alternator tested. It checked out okay at that time, but now that the lights are constantly dim, I'm going to check it again. I put on a set of shims on their recommendation because the terminals were a bit loose and stretched out. Said alternator was also replaced several months ago.

- A couple of months ago, we changed out a bad console. There may be a short there, but I would have thought that it would cause other more noticeable problems than a voltage drop.

- Somebody has used one of the available plugs on the fuse panel to run a live wire to the aftermarket stereo. My brother in law said that wasn't his doing, but I don't think that was the issue.

- There is an "extra" yellow wire behind the stereo that's thoroughly taped over, I'm not sure what it's for. We had to tape it down again recently because it was shorting out the stereo, but when it shorted, it would only kill the audio. The rest of the electrical system worked fine anyways.

My brother in law suspects a bad ground, but I have no idea how to hunt anything like that down. I've been over the engine compartment numerous times, and I still can't find any loose or exposed wires, or anything that screamed "problem" at me. Ideas?

 

Okay, scratch on the whole "I drive it x miles without a problem" thing. Just drove it home from work. I noticed that the speedo cut out whenever I signaled. Got home as efficiently as I could. The lights dimmed to almost nothing, and I got it in a parking spot and let it run for a minute. It didn't cut out on it's own, but it won't restart. Looking more like the alternator?

Could a bad alternator test as good if the voltage regulator was screwing up?

 

The voltage regulator is "built into" the alternator. Typically replace both as a unit (when you buy a new alternator, it comes with regulator).

Also the alternator controls the "battery" light on the dash. It's really showing alternator performance not condition of the battery.

To test further you will need a volt/ohm meter. Testing the voltage at the battery with the engine running will show the overall charging performance. That is basically the test that the parts stores do.

If the alternator belt is OK, I'd suggest just replace alternator at this point.

 

Thanks, mk. I bought a multimeter, and yes, there is no charge coming from the alternator. So, my brother in law is going to help me swap it tomorrow.

Meanwhile, I followed the Hayne's guidelines for testing the charging system, which included putting a test light between the negative post and the terminal while the key was off. I bought a test light for that purpose, and it blew it out. So, I assumed there was a short and went to the next step. Except, I couldn't just see when the test light dimmed, so I used the multimeter to look for voltage. The ECM was holding 10 volts. I didn't want to check the amperage since I couldn't be certain that it wasn't drawing more than 200 mA. Does anybody think that's a problem? The ECM should be drawing power, but is 10 volts too much?