I just finished replacing the battery and alternator in my 79 F150, the old alternator had shot, screechy, bearings. The truck fired up instantly even though cold, and the new alternator is definitely quieter (as it should be), but now the ALT light is on steady. I *THINK* I hooked up the 3 wires correctly, and I double-checked the belt tension, but admit I neglected to take a picture of the wiring before removing the wires from the old alternator.

Help! I haven't replaced an old alternator in 25 years or more, so my troubleshooting skills aren't very good.

Thanks in advance!

 

I would look at the wire colors at the ALT an what studs they go to (letters or marks) and then look at the regulator and the colors on it and what they go to (letters).
I think the regulator and ALT should have a "I" and a "F" the wire colors should go to the same letters at both ends.
The big stud should go to the battery side of the solenoid.
It could be you got the 2 smaller wires at the ALT mixed up and not charging OR the regulator is bad?
Just be careful as 1 of the small wires could be a ground and not "I".
Dave ----

 

Do those colors help? I went out to take a pic of mine on my truck, but it was dark and under two heater hoses, and is some grungy. My '77 still has it's OEM 60 amp alternator in place, I had this pic on my PC labeled as correct for my truck.

 

 

It finally warmed up enough to work outside on the truck. Problem solved. I had the stator wire on the ground post. The truck runs great again, and no more bearing screeching. Thanks to everybody who posted on this thread!

 

Just completed an alternator swap on my F-350. 60A Alt here too. Pic for fun.

I took the pic before I removed the wires.

 

That wire looks like its ready to break.

 

Yes...I noticed that too. Thanks. Haven't had time to get back to the truck...I'm full steam ahead on my winter hobby. 🚂🚂 (not trying to hijack the OP's thread.)

 

That's n awesome hobby!!

 

I’m curious about this subject. With most parts nowadays being built like crap, does anyone get their alternators rebuilt?

I hope in six months I’ll be at the point to worry about this. When I’m ready, I’ll need a new wiring harness also. I’ve read about the 3g alternator upgrade, but I’m not sure if I’ll go that route.

I bought a new ‘88 F150 in late ‘87. I didn’t have AC, so it got dealer installed AC before I picked it up. The alternator went just out of warranty. I found out they never changed the alternator to a higher amp. The only one I could get to match the mounting was the same smaller alternator. I ran that one for a year or two before it crapped out. On recommendation of a friend, I brought it to a guy that rebuilds them. He turned mine into a high amp one. That alternator was still in the truck when I junked the truck almost twenty years later. The truck was my daily driver for just over 25 years.

It looks like the company is still in business. I was thinking of bringing my alternator to him for a rebuild, whether it needs it or not. The alternator has been unused in the ‘77 for the last twenty years. I doubt it was the original. But maybe the remanufactured ones back in the day were better? I’d rather not have to worry about a bad alternator the day I break in the cam.

What’s everyone’s thoughts? 3G, todays remanufactured, or locally rebuilt?

 

I bought a rebuilt started from a "reputable" rebuilder and after the second rebuilt from them I ended up buying a new started from rockauto.com.
I also bought a rebuilt alternator from them too that is starting to give me issues so I'm going to buy a new one from rockauto.
60 amp for $85 including shipping.
I'm done with rebuilt alternators and startes.

 

I had my alternator on my 78 F250 rebuilt, just because it's a larger alternator that came with the camper special package. They were also able to raise the output voltage to 100 amps.
I have an E350 that the bearings in the starter have been squealing in the colder months. I'll probably pull that and take it to them also.

That nearly broke wire looks like it might have been the problem with that alternator.

 

Surprisingly...no. The bearings were ruined after getting bathed in antifreeze that resulted in an intermittent deafening high pitch sqeal that was so loud my wife heard it when she was following me on a trip to town a few weeks ago.