Wiring question; Volt Gauge/Hazard

[rsicard]

When things get confusing, go back to the basics. The most mysterious problems revolve around the grounds or as I call them, RETURNS because this is the other 1/2 of the complete circuit the ground or return side. Run a heavy gauge jumper from the case of the alternator to the heavy gauge termination of the negative cable from the battery. Don't assume there is a good conduction path from the alternator case (negative side) through the engine back to the negative cable attached to the engine. Then retest the alternator and proceed with troubleshooting if needed.

[rfaranda]

When things get confusing, go back to the basics. The most mysterious problems revolve around the grounds or as I call them, RETURNS because this is the other 1/2 of the complete circuit the ground or return side. Run a heavy gauge jumper from the case of the alternator to the heavy gauge termination of the negative cable from the battery. Don't assume there is a good conduction path from the alternator case (negative side) through the engine back to the negative cable attached to the engine. Then retest the alternator and proceed with troubleshooting if needed.

Just jumped the case / negative terminal... Same results...:disappoin

12.4v +/- at S, L and B...

I turn on everything, radio, lights, heater.... It drops to 11.8 +/- and maintains.. I pull the negative cable from the battery, the car stays running and you can hear the alt kick in..

[Zed Head]

It's not recommended to remove your battery cable like that, but since it's done and the car stayed running, it is obviously producing electricity.

Is it possible that you have actually corrected all of your problems from the first few posts, with the wiring and the bad alternator (you did make some wiring fixes and the alternator is new now), and that you've been trying to verify the repairs with a bad voltmeter? Maybe everything is now working correctly.

Might be worth driving to a shop or the parts store and getting a second opinion, with a second set of diagnostic equipment, on the running car.

[rfaranda]

It's not recommended to remove your battery cable like that, but since it's done and the car stayed running, it is obviously producing electricity.

Is it possible that you have actually corrected all of your problems from the first few posts, with the wiring and the bad alternator (you did make some wiring fixes and the alternator is new now), and that you've been trying to verify the repairs with a bad voltmeter? Maybe everything is now working correctly.

Might be worth driving to a shop or the parts store and getting a second opinion, with a second set of diagnostic equipment, on the running car.

I wish it would be that simple... I took it down to Autozone and had them test it in the car. Theiir tester kept telling us to start the car (and it was running) ....

[SteveJ]

Actually, I don't trust the chain stores electrical testers. About 15 years ago, a friend said the Lamp light was on in his car. I suspected a bad internal VR. The chain store said the alternator was good. I said BS. He got another alternator, and the idiot light wasn't lit anymore.

[grantf]

I will try again.... Is you're battery good? are ALL of the contacts clean? not just the terminals but ground contacts???

[rfaranda]

I will try again.... Is you're battery good? are ALL of the contacts clean? not just the terminals but ground contacts???

Sorry, I missed your first post.

Yes, I've run new wire from S to battery pos, B to starter and jumped ground to neg. L is showing 12v and the charge light works normally. This is the second battery.

I am really thinking the new alt is bad even though they tested it (and I watched). I went back tonight and had them test it in the car and it wouldn't push over 12.33v.... UNTIL they pulled the postive battery cable while testing and it jumped to 14.55v. I'm thinking the voltage regulator isn't detecting the battery properly.

[FastWoman]

Twice I looked at this thread and thought the problem was solved! But since it's not, I'll pitch in too...

Let's simplify a bit. Disconnect your (-) battery cable, disconnect the big wire from the B post, and keep it safely out of the way. (Wrap with a bit of electrical tape?) Reconnect your (-) cable, and start your engine. You should get 14.5V from the alternator, give or take. This is your alternator's output when not under load. It should reflect what the integrity of the voltage regulator.

Next connect a heavy piece of wire from your B post directly to the (+) terminal of the battery (remembering again to pull the (-) battery cable to do your wiring). Start your engine again. You should still get maybe 14.5V at the B post. If you're still getting 12.5V with that setup, either your alternator isn't putting out adequate current (my guess), or something is wrong with your battery (unlikely).

If your alternator and battery work, then the problem is somewhere in your car's wiring. The more likely guess would be a fusible link issue (still), but if that's not it, take a look at the alternator-to-battery wiring. If you unwrap the wiring harness between the alternator and the fusible link assemblies, you'll see a scary mess of funky spliced wires (spliced at the factory). You could beef up those wires and connections.

BTW, the alternator and fuel pump do interact on the later models. The alternator output and oil pressure signal feed to the fuel pump control relay to signal that the engine is running. If both of these signals fail, the fuel pump is shut off.

Also the 12.5V reading at B and S, compared to the 12V reading at L is normal. B and S have a direct path to the battery, while L has a semiconductor junction inbetween, thus dropping the voltage by about a half volt.

Edited February 25, 2011 by FastWoman

[rfaranda]

Twice I looked at this thread and thought the problem was solved! But since it's not, I'll pitch in too...

Let's simplify a bit. Disconnect your (-) battery cable, disconnect the big wire from the B post, and keep it safely out of the way. (Wrap with a bit of electrical tape?) Reconnect your (-) cable, and start your engine. You should get 14.5V from the alternator, give or take. This is your alternator's output when not under load. It should reflect what the integrity of the voltage regulator.

Next connect a heavy piece of wire from your B post directly to the (+) terminal of the battery (remembering again to pull the (-) battery cable to do your wiring). Start your engine again. You should still get maybe 14.5V at the B post. If you're still getting 12.5V with that setup, either your alternator isn't putting out adequate current (my guess), or something is wrong with your battery (unlikely).

If your alternator and battery work, then the problem is somewhere in your car's wiring. The more likely guess would be a fusible link issue (still), but if that's not it, take a look at the alternator-to-battery wiring. If you unwrap the wiring harness between the alternator and the fusible link assemblies, you'll see a scary mess of funky spliced wires (spliced at the factory). You could beef up those wires and connections.

BTW, the alternator and fuel pump do interact on the later models. The alternator output and oil pressure signal feed to the fuel pump control relay to signal that the engine is running. If both of these signals fail, the fuel pump is shut off.

Also the 12.5V reading at B and S, compared to the 12V reading at L is normal. B and S have a direct path to the battery, while L has a semiconductor junction inbetween, thus dropping the voltage by about a half volt.

Ok, heres what I got:

1. B disconnected 17.85

2. B direct to Pos. 12.36

I'm headed out for a new Alt....

[rfaranda]

Lesson learned: Don't always trust Autozones testing!!!!!!

New alternator did the trick... She's running like a champ.

Thanks to everyone who helped us out with this. My son and I are very grateful. Even though it ends up that we wasted A LOT of time on this, the knowledge we've gotten gained is invaluable.

[rfaranda]

Actually, I don't trust the chain stores electrical testers. About 15 years ago, a friend said the Lamp light was on in his car. I suspected a bad internal VR. The chain store said the alternator was good. I said BS. He got another alternator, and the idiot light wasn't lit anymore.

Any of you guys (and gals) find your way to Central Alabama, the beers on me!!!

[FastWoman]

Sure thing! Glad you got it straightened out.