ALT issue

[Trollhole]

Well my gremlins still are getting me. After my stock alt died early last year I upgraded to a one wire GM alt. Then went with a dual battery setup with an isolator. This is when my problems began. The alt wouldn't charge the batteries. I ended up taking it back to the alt shop and they rebuilt it again. A month later I went on a wheeling trip and needed to use the winch and found out real quick it wasn't charging either battery suffeciently. So I ran the two optimas in parallel and ditched the isolater. Now one month later the alt is not charging. It's only putting out like 12.4 -13 volts. I've only have one wire comming from the alt going to the batteries. How could I be screwing up something?

This pic is before I took out the isolator but gives you an idea of where I'm comming from. I have trouble shot this crap so long that my head hurts. And I consider myself pretty good when it comes to electronics.

 

[Big B.]

Which alt you got, Whats the output?

 

[Pin_Head]

One wire alternators are drop dead simple. If the alternator is good (pretty likely since it has been in the shop) all it needs is a good connection to the battery and ground. Check for a bad ground by running a jumper cable from the case to the - side of the battery and see if the voltage jumps up. Do the same with the B+ and the + battery post.

Are you sure it is really a one wire alternator? These only have the wire to the battery and do not require an igniton on wire.

 

[Trollhole]

Yep I told the alt shop I only want an internally regulated alt with one wire.

The ground is a good idea I will try that. I have seen stranger things. If not I'm going to take it back and have them look at it.

 

[Pin_Head]

It looks like a Delco 12Si. Most of these are two wire, but they did come in one wire too. Does it have a connector on the back besides the B+ lug? One wire units need to be revved up before they start charging. Alternatorparts.com FAQ says that most one wire alternators can be used in a two wire mode with a wire to the ignition "run" switch so that they will start charging at low RPM.

 

[Trollhole]

interesting.

 

[Benson]

I've had a similar problem lately. Nothing like having your duel-battery setup leave you stranded from a dead battery

I had a bad regulator in my brand new high-output alternator. Makes you miss Toyota reliability.

 

[Trollhole]

One wire alternators are drop dead simple. If the alternator is good (pretty likely since it has been in the shop) all it needs is a good connection to the battery and ground. Check for a bad ground by running a jumper cable from the case to the - side of the battery and see if the voltage jumps up.

That was it. Bad ground. I just never thought it would be that. I had tried everything else. So I have run a ground from the alt the the ground on the frame. Works perfect. Thank you. No more battery problems and I can use my isolator now.

 

[Pin_Head]

Congrats.

Just a heads up: If your alternator wans't well grounded, chances are that your engine isn't either. Make sure that you have a good ground from your starter or engine to the frame.