Big Time Alternator Problems

[CaptRoy]

My battery went dead so I pulled it and I took it to Autozone. They said it was bad and would not hold a charge. It was only 6 months old so I returned it to Sams and they gave me another, exchange, but said the battery had been discharged to much causing it to fail.

I put the new battery in but, I suspected that my alternator was not putting out.. So I checked the voltage on the battery before I started the car and then with the motor running... Both read 12.4.. I just knew I had a bad alternator even though it only has about 500 miles on it.

I pulled the alternator Tuesday night and dropped it at an alternator shop. Went back yesterday to pick it up and they said there was no problem with it... Putting out 14 volts.

I put it back on the car last night... read the voltage before I started it and it was 12.4 and after I started the car it was 14.0... Yea working!

I wanted to drive it to work today... Started it up and the red light did not go out... I reved it to 1500 rpm and the light went out, off to work I headed. About a 1/2 mile from the house the red light came on again and stayed on until I put it in the parking lot...

I must have something like a loose connection... Not an easy thing to find..

Any ideas where to start...

 

[Andrew Mace]

Any and all grounds relative to the charging system? Especially battery connections? Just a thought....

 

[martx-5]

What car is this for??? Do you have an alternator in the TR3?? If so, which one???

 

[CaptRoy]

Art,

Yes I put an alternator in the TR3...It's a Delco.. Andy, good idea.. I'm going to start chasing everything down this afternoon...

 

[Aldwyn]

Bad belt, per chance? Maybe the belt is slipping...

 

[kodanja]

Really sounds like a bad ground

 

[PeterK]

I suspect that you're getting resistance from the starter to battery ground so that you're not getting enough amps spin the starter. Check and clean the grounds.

For neg- ground :

The ground cable from the battery should go to firewall (body) above and behind the battery towards the brake master. Tighten both ends, make sure that the battery post and firewall is clean and the threaded hole on the firewall is clean.

Engine to chassis ground is a bare braided cable. It is connected between a 5/16" bolt through the front engine plate above the motor mount and connects to the rearmost engine motor mount bolt. This cable passes the connection around the rubber engine mount because the rubber insulates the engine ground from the chassis. Same method used on the steering u-joints.

Anyway, this completes the starter circuit to ground between the starter to the chassis, to the firewall, and finally to the battery. Hope this helps.

 

[martx-5]

I'm assuming that the Delco alternator you have in there is the 10SI unit (7127) that has an internal regulator. If so, these units are pretty bullet proof. According to all of the symptoms you've described, I'd have to go along with the loose belt diagnosis. Alternators need more belt tension then generators, especially at lower engine speeds and because of higher output capabilities.

This dosen't rule out any funky electrical connections, but you really only have several to worry about concerning the charging system.
1. A good ground from the alternator back to the battery. This is handled through the casing and engine. But, on the TR3 there is the ground from the engine to the chassis with a braided strap down by the left motor mount.
2. A good positive connection from the alternator back to the battery. You probably have it connected to the starter relay up by the firewall.
3. The two wires that plug into the regulator in the alternator. One of those is most likely routed right back to the output terminal at the back of the alternator. The other one goes to the dash light. The dash light circuit seems to be working fine.

Tighten the belt first, and if that doesn't do the trick, go through the wiring I mentioned.