My brother-in-law has a '93 Bronco. The alternator died, confirmed by testing at NAPA. He bought a new (rebuilt) one and installed it. When he first put it in the charging gauge on his dash showed briefly a few minutes that it was charging good, then after that went right back down to barely showing it was charging (below the "normal" charging indicating area on the gauge, and staying there). So it seems definitely that it's not charging, something is wrong. All wires and connections are clean tight and seem sound. The belt is tensioned good, that's not the problem. So what the heck, any ideas why the new alternator isn't charging?

 

Internal or external regulator?????

Ford had a problem with the alternator connectors Burning up......They sometimes--(But not always) gave you a new "Pigtail" to splice in...

 

internal regulator (fairly certain). So this alternator connectors you mention, which connector and how would I tell whether it burned up? Do you mean they would burn up on a new alternator too? They didn't give any pigtail with the new alt he got. Could you elaborate a little more, if possible? thanks

 

Ok ....

Internal regulator will have a Flat black plastic "BOX" bolted to the rear of the alternator.

On top will be a a "Rectangular" wiring connector, about 3inches by 1/2 inch wide......with 3 wires....Black/orange, black, and a white with a black stripe.

Then of course is the Battery lug, or OUTPUT lug

Its time for ALTERNATOR 101........
The alternator charges your battery, and in order to do that properly it must know exactly how much of a charge the battery presently has. Too little charge leaves you with a dead battery, too much and the battery cooks itself and explodes.

Having said that... That connector at the top of the alternator is responsible for supplying voltage to the alternator to allow it to perform its function, and The "STATOR" line, which the regulator uses to compare input and out put voltage and amperage. If the connector were to fail, as was common, The alternator cannot compare the present voltage and current, to the "Target". It then produces excessive amounts, with no where to send it, and it burns up. There have been quite a number of cases,(I have personally seen 8 or 10 myself) where the alternator actually bursts into flames.
Anything that smells of BBQ hot dogs is a reason to instantly shut her down.

 

It is definitely the internal regulator, as described.

And, according to my brother-in-law, the story is as follows: He was driving along and his lights started flickering, etc., so he pulled over to look under the hood, thinking maybe he broke a belt or something. No broken belt, but the alternator was making unusual noise and was "red hot" to the touch, he said. He drove it a short distance to get home, and the next day took the alternator to NAPA where they tested it and said it was dead. He bought a new rebuilt one and installed it, only to find that it did not seem to be charging the battery, as the voltmeter in his dash stayed down in the low area as he drove around. He figured he should put the battery on a charger, and took it out and did so for a full day on a "trickle" charger. After the battery charged and reinstalled, he saw that the voltmeter needle in the dash showed good charging going on while he drove around, but that a few times when he drove on a rough surface or hit a little bump the needle would go back down into the low zone and stay there until he hit another bumpy surface and then it would go back up and stay there. As though hitting bumpy surfaces would maybe be jarring a loose connection. He double-checked all alternator connections noted all seemed fine except one apparent "black single wire" to the alternator has "sort of bad clip" or "tab", (not sure what he means, maybe a terminal) but that its been that way for a long time. So he said he'll get a replacement for this and then see how it acts. I asked him how the connector looked, he said fine, and said he wished he could afford to buy a new one right now but can't because the replacement alternator broke him, and he's hoping replacing the inexpensive single wire will solve the problem. comments/advice?

 

To the tune of?...................................

 

It was to the tune of $135.

 

If the headlights were flickering then I think you have a live short somewhere.
If the alternator failed then the lights would run off battery power and go slowly dim as power got drained from battery and the voltmeter would go down slowly.
Could take 15 to 120 minutes for the lights to go out depending on the loads and the size and condition of the battery.
For the voltmeter to be good one moment then take a nosedive then be up again it would be a intermitant short.
Likely in the lights because they are flickering.
The headlights dont have a fuse to open like most devices do when there is a short because they dont want you to be without lights all of a sudden. The circuit breaker will reset itself to give you enough time to pull off the road.
Can you hook up an ammeter and see what the draw is when the lights flicker?
A heavy draw can toast the old and new alternator
This is why there is a no return policy on electrical parts in most places

 

$135 is actually pretty cheap. Normally NAPA is more than others around here. Autozone shows a Rebuilt unit at $160....and a new one at $155? WTH is up with that?

 

He got it from Schucks, even though NAPA tested the old one for him. NAPA was going to cost too much

NAPA is normally more expensive around here too. I suppose he was lucky to find one for $135. And that sounds totally screwy, why would a rebuilt cost more than a new? Crazy man crazy

 

Thanks for that explanation. The revised story now is that the lights were not flickering, but going dim as he was driving along. Insofar as the return policy for the alternator, apparently they told him it has a warranty for a certain amount of time (can't remember how long) so maybe he could return it if he thought it was bad.

 

sometimes you get a bad alternater, would probably go have the battery and alternater tested.

 

Not to take you off track...but back in the day, had a Honda Civic with a partially broken lead from alt to the battery. No volt/amp meter, just idiot lights. Lead would test fine engine off or at idle..but when reving down the road, would open up lead and cook the alt. As said before..calling for juice, nowhere for it to go.

Ate 2-3 alternators (ha! love the warranty exchange thing) before I broke down and took it to a shop...30 min and $40 bucks later..all was well.

When the alt is super hot..its most likely a wiring issue.

 

Its Easy to do and I have caught myself doing it too but a good ground is just as important as good positive connections easy to check with any ohm meter just go from the battery Neg. to the altenator housing it should read 0.00 if it reads any resistance at all then the connections on either the battery or where it connects to the engine block is corroded/loose and should be corrected to get proper operation of the electronics. Make sure you are making contact with the battery post itself and not just the cable clamp when checking otherwise you are bypassing the connection to the battery itself.

 

Thanks hickwithstick. We'll check that for sure, especially since it's easy to check as you described. Will post back if any "interesting" results.

 

the motor needs to be running when performing this test. RW

 

Okay. Thanks retired wrench.