I didn't know where to post this, so instead of making a new thread I figured I'd post it here. Swap has been running great for a few thousand miles. A new problem has come up though.

I had the alternator from the 3.0 rebuilt and am using it on the 3.4 engine. Recently the charge/brake light has been coming on randomly and the volt meter drops to around 12ish volts when it happens. It only does this when warm. I figured it was the belt, so I tightened it, but the problem still persists.

To pinpoint it as an alternator problem, I waited for the lights to come on, pulled the positive terminal and the truck died. In the past this has always indicated a bad alternator, but seeing as this one was just rebuilt, I want to rule out any other problems before I pull it and take it back to the alternator shop.

Any ideas what could be causing this besides a bad alternator?

Thanks in advance!

 

Can you borrow an alternator from another truck to test it?
I think Sears also can test your alternator.

 

I think autozone can test the alternator as well, but generally from what I can remember electrical problems get worse when it gets hotter.

Also:
http://www.youtube.com/watch?v=FTGz0...ure=plpp_video

 

Alright, I have run all of the tests, taken the alternator back to the shop that rebuilt it (said it was okay), and replaced all of the positive and negative cables in the truck. Still no change.

Just a shot in the dark, but is the alternator voltage regulated from the ECM. At the batt terminals, the voltage is 14v when first started, and then dips down to around 11.8 volts after a min or so. This causes the batt and brake lights to come on. Then it cycles between 11.8 v and 12.5 volts, which causes the two lights to go on and off.

Any other ideas guys, I'm about to go get another alt to try out.

 

do you still have the alt from the 3.0? You can swap the rear plug and heatsink.

 

Well, the alternator that is on it is the one from the 3.0. I have sourced one from a 3.4 that I am going to get tomorrow, so hopefully that will fix my problem

 

new alternator fixed it. Another question though...the fusible link in the 98 that i pulled the thing from was 100A and the one in my truck is 80A. Is this going to cause an issue?