I've been having charging issues with my alternator, in that it generally does not charge the battery, and occasionally, shortly after startup or after running for some time it will start to charge normally for a few minutes, and then stop again.

My truck is a '93 f150 with 4.9l, and I have a 95 amp 3G alternator from PA performance that I installed with their kit nearly two years ago.

Here is what I have tried:

1. Checked voltage outputs going into the alternator with ignition on, everything checked OK. checked voltage across battery and at the connections, again everything generally fine... except that while running the voltage across battery reads ~12.5 when it should be ~14.

2. checked grounds/connections... i at least visually checked all of the grounds I could think to and everyhting looks fine, no excessive corrosion or anything that might lead me to believe there is a bad connection.

2. new battery

3. Sent alternator back to PA performance, they repaired a loose connection somewhere and sent back. still same problem.

At this point I think it has to be a loose connection somewhere, but I'm not sure where to check at this point... I think I've already gone through the obvious checkpoints, and everything seems ok. And since its already been sent back to PA, i'm assuming the alternator itself is fine.

Any one else run into something similar to this? any help is appreciated.

 

Go to all the terminals that go to the alternator on both ends, and remove the wire, clean it with a wire brush, then reterminate snuggly. Then see what you got.

 

The Light Green/Red wire is the "Exciter Voltage" feed. This is what turns the alternator ON for all practical purposes. I would start there.

 

I had a very similar problem with my Escort. Turned out that it was a bad tensioner for the serpentine belt. It would occasionally slip enough to drop the voltage.

 

zxwut?---- will give that a try.. a bad connection could be a possibility.

rla2005---- i've checked this wire at the point where it connects to the alternator and it reads around 12V, which i think is what it should be at. Since you brought this up, I'm thinking it could be loose and when I originally checked this voltage it was connected, would explain why it read correctly and why the alternator someimes works.

SGT Neutron--- How can you tell the tensioner is bad? I would assume that if it was bad it would pull off of the belt fairly easily? Mine seems to put a significant amount of force onto the belt, similar to what it has done since i've owned the truck.

further on the tensioner note, coudl it be something with the pulley on the alternator that its not spinning properly? is it all right to spray wd-40 or pb blaster or something on there?

will update after checking these.

 

well, after double checking everything i thought could be wrong with my electrical system, I cracked and bought a new alternator and everything worked fine.

After this I sent back the old alternator to PA Perf, and they did a few more tests on the thing, and everything still checked okay. So really still no idea what was wrong with it. I will say they were a great company to deal with... despite everything checking okay on their end with the alt, they sent me another new alternator, put it in this week and am back up and running.

Thanks for the suggestions.

 

Thanks for the feedback!

I recently had an issue with the exciter wire connector to my newly installed 3G alternator from RJM. Long story short the connector RJM supplied was bad, the wire crimp was less than stellar. As I drove down the road the 12V that supplies the turn on voltage was losing contact. All the lights flickered off/on, the tach started jumping around and the fuel gauge on both tanks read way passed full. Once I got home and placed a meter on the battery I saw the alternator output was zero. I pulled on the green/red exciter wire, it pulled out of the crimp.

As much as I wanted to call Ryan and jump his case, I decided to repair it myself. All is well with the world now.

 

It sounds as if the brushes inside on the rotor are bad / worn out. Or maybe a bad spring on the brushes. I had one doing pretty much the same.. opened to find the brushes are just about gone.

Glad to hear they sent you another alt that fixed the problem.