legacycentral bbs

Ok weird problem. It seemes like my alternator is doing nothing. It's not charging the battery (which I had tested) and the car can't run off it. I had my old alt tested and it's numbers were low so I replaced it. I charged the battery up to give it a fresh start and the problem just repeated itself. As the power lower I start getting what feels like fuel cut when I try to accelerate once the boost starts to build. It'll will operate normally for a while at low RPMs but if I keep trying to drive it it eventually just runs out of juice and dies. The ABS light has been on since I replaced the ABS pump about 3 weeks ago. I was having an issue where it wouldn't shut off when I turned the car off so I just unplugged it for the time.

Anyway, any help or ideas about where to go from here would be great.

You don't mention what time scale this stuff is happening on. Is it possible that your alternator is working but the battery is being drained when the car is parked? Or do you mean that the freshly charged battery discharges after like half an hour of driving?

Is your battery/charge warning light in the dash on? And does everything else work (particularly your horn, brake lights, HVAC blower, and power locks)?

The thing you're experiencing that feels like fuel cut is probably just misfire. You're probably getting a spark that's strong enough to ignite the relatively light air/fuel mixture at low loads but not enough when the cylinders are packed with air and fuel at high pressure.

If you don't have a voltmeter, this might be a good time to buy one. You can check for sure whether the alternator is charging or not by doing this:

Turn the engine off but leave the ignition switch on.
Turn the headlights on for 30 seconds and then turn them off.
Measure the battery voltage.
Start the engine, wait about five seconds, and measure the battery voltage again.

If the measurement is higher the second time around, your alternator is charging the battery. If it's the same or lower, it's not.

The next check is to unplug the harness connector from the alternator and check each of the wires. The white one should have +12V on it at all times (this is how the alternator's voltage regulator knows what the current voltage is) and the yellow one should have +12V on it when the ignition switch is on (this is what activates the alternator's field coils).

If both of those have power when they're supposed to, all that's really left to try is connecting the battery terminal (the one attached to the two heavy white wires with ring terminals) on the alternator directly to the positive terminal of the battery. If that makes the alternator start charging the battery, you have a fault in the wiring between the alternator and the fuse box.

If this is a rebuilt aftermarket alternator, don't be surprised to find it bad.

Timescale...

A freshly charged battery discharges after like half an hour of driving.

It slightly complicates things that this is all going on while I'm couch surfing between apartments, street parking in SF.

The battery/charge warning light I don't believe is on. Again the ABS light is constant when on but that's been an issue for a while.

The whole car looses power. Lights dim, radio cuts out, wipers slow down. It's a gradual loss.

And ya it might be volt meter time

Ah, then, yes, it does seem that the alternator's not charging.

Steve's right -- it's scarily common for third party "remanufactured" alternators to be bad out of the box. I've had it happen twice.

Other thing to note is that if your battery is a regular battery, having it fulling or nearly fully discharged will shorten its life and it will not hold a full charge well. So if you find the problem to be the alternator, don't be too surprised if you have to replace the battery a couple months or so down the road.

it's a Yellow top. But ya It's something I was aware of and had it checked before shelling out for the alternator... and ya I know this may have messed it up.

I'm going to see if it's got enough juice to drive to a car parts store in the city today and get the alternator... you know, sticking to the side streets in case everything fails.

If it's an optima yellow top, you should be fine. Those batteries can withstand numerous discharge cycles.

It's also the length of time of discharge. The longer they sit discharged, the less likely they'll be any good. Sometimes overnight is enough, but can't say anything specifically about the Optima.

The other thing I've found is that it seems a lot of the guys who test the charging systems in chain mechanics places don't know what their doing/how to use the equipment and give false OK's to the alternator. To be fair, the problem can be intermittent, like cold solder joints on a diode pack might cause.

Hey Guys. It was in fact a bad manufactured alternator. Had them test it where I bought it and it was worse then the one it replaced. Swapped in a new one after driving across town on a fresh charge to a different store. Made them test that one before I left

Glad it works now. Good call, Steve.