Hot Rods Alternator, electrical question

Hi to all. Long time no problems, now I have one. On my Buick station wagon I replaced the water pump and fuel pump because it sat so long. I got everything back together and fired her up and the alternator started squealing , I thought it had bad bearing in it too from sitting. I put in a new alternator and it did the same thing. There are 2 wires going in to the post on the back of the alternator, one brown{its thin} then there is the big red wire. Now when I turn the key on the brown wire has power but the red wire doesnt{even when it running}While the car is running I hooked up the brown wire, and it runs fine but when I hook up the red wire it starts squealing like crazy and acts like a load is drawing it down. It ran fine before I replaced the water pump and fuel pump. Do you think I may have a dead short in the red wire some where?. Ideas welcomed. Thanks Bruce.

 

The brown wire is most likely the exciter/field wire, to #1 terminal on alternator plug. Then the big red power one at terminal #2 should have a jumper to the battery stud on the back of the alternator. I would trace that red wire back as far as possible to see it is touching ground.

 

That's what was afraid of.I wonder why it just starting doing it.Thanks Bob. Bruce.

 

Trace your steps backwards, anything to do with the water pump that may have gotten pinched? Was the starter out of it? Engine jacked up off the mounts?

 

Tighten your belt just a bit and see if it quits. If it hasn't been run in a while the battery may be taking a heavy charge and putting a big load on the alternator.

 

I don't think you have a short to ground, or it would be going up in smoke. The other end of the wire connects to the battery, so it is seeing full battery voltage all the time. Any short to ground would have that wire smoking big time. I agree with Ebbsspeed, tighten the belt.

 

Maybe some antifreeze or something got on the belt in the process of changing things?

 

Some of the '70s GM cars had pretty high output alternators for the belt driving them (should have had 2 belts) and if the belt isn't tight enough it will slip if the alternator is trying to charge up a low battery. As the others have suggested, tighten the belt.

 

Is the battery low? Charge it up good with a charger. It takes hours for an alternator to get them plussed up and is hard on them. I can still hear in my mind the groan of a jump-started car alternator in -10° below weather.

 

I agree, you've changed the belt tension when installing the other items.
Tighten it and if it doesnt change loosen it.

 

My guess is when the main wire is disconnected the alt. is freewheeling. When hooked up the alt. is working and therefore needs more effort to turn it. When it's squealing, squirt some soapy water on the pulley and if it stops squealing it means the belt needs tightening.

 

It takes one husky battery charger to equal the output of even the wimpiest of alternators, and I don't agree with it being hard on the alternator. In most cases the alternator will charge the battery completely long before your typical "traditionalist's" battery charger will.

It does sound like you might have a short, because there should be 12 volts on the big red wire whether it is disconnected or not. Connecting it would put a big load on the alternator if it were shorted. If the engine is running you should have more like 14 volts on the post on the back of the alternator.

 

The big red wire is the output from the alternator. It should have full battery voltage at all times. Trace that wire and find out why it has no power.

Sent from my SM-T350 using The H.A.M.B. mobile app

 

An alternator is quite capable of charging a low battery. Problem with that is it isn't really designed to do that along with supplying the car's other electrical requirements. Using the alternator to charge a low battery may shorten the life of your alternator. Use a battery charger to charge the battery and run the vehicle with a fully charged battery unless you just have no other option.

 

Put a good charge on the battery and tighten the belt Bruce. you may have two issues one a low battery and a loose belt combining to make the alternator squeal. If that doesn't cure it check the battery for a bad cell. Joe

 

Can some one explain how running a alternator at a high charge rate will shorten the life of the alternator.

 

I've been in the auto repair business for 40 years. I've been to many workshops and seminars put on by rebuilders and they all have said many times that an alternator is only designed to maintain a fully charged battery, not charge a dead battery and supply the electrical needs of the vehicle at the same time. An alternator charging at a high rate long enough to charge a dead battery will create enough heat to damage the windings in the alternator (burn the insulation off the windings). Ask any knowledgeable rebuilder, mechanic or parts person and you'll get the same answer.

A quick internet search: https://www.optimabatteries.com/en-...nators-are-not-designed-charge-dead-batteries

I'm sure you can find other information out there to support this.

 

Hey Bruce. What is battery voltage w cables off, fully charged? Good advise to follow the big Red wire to next connection, test for voltage there. Where does it connect? Should be battery voltage.
Once you figure out why there is no voltage at Red to alternator, disconnect brown, connect Red, and fire it up. No screeching? Then touch brown to it's connector on alternator. That should be like switching on the alternator to charge. If it screeches, check belt tightness.

 

BossBob, I never had the starter out and never jacked up the engine.I am still searching what it might be.Thanks Bruce.

 

Thanks Ebbsspeed, I will try that.
Thanks.Bruce.

 

Blue4U I will try it but I don't want to burn out the bearings out of the alternator. Thanks Bruce.

 

Rjones, I cleaned the pulleys and am on my 3rd new belt. Thanks Bruce.

 

Thanks I will give it a shot. Thanks Bruce.

 

O.K. Thanks Joe It was a new battery in April but who knows now a days.LOL.Bruce.

 

Ebbsspeed, shouldn't there be power to that big red wire going to the alternator when the engines running even if its disconnected from the alternator??? Bruce.

 

Goldmountian, looks like that's what I am going to have to do. Boy that's going to be fun. LOL. Bruce.

 

Rfaze,thanks you have always helped me out with electrical problems before.Thanks.Bruce.

 

Are your belts maybe just a skosh too long and you're running out of travel on the adjustment?

 

An alternator can take a low battery to full charge without hurting it. You just don’t want to do it every time. As stated it’s job is to maintain a fully charged battery. But upon occasion it can do more.
It’s just like your engine, it’s job is to take the car down the hiway at 75 mph and can do that for 250,000 miles. It can also take you down the 1/4 mile drag strip in 12 seconds, but it won’t do it a million times.


Bones