Any insight on this would be greatly appreciated...

I threw a 130 amp alternator on my truck that I bought online. Mine came with a 105 AMP alternator. I threw it in correctly without damaging anything and even put the appropriate belt on to match. (the 130 amp alternators need a slightly bigger belt I guess) So everything went fine, drove it around town with no problems. Then I get on the highway at night and I notice my lights flicker randomly as I drive around 2000 RPM. They dim like the truck was shut off then get bright again, for like a split second while I am driving. So I called their tech support and they didn't know what was wrong so they sent a new alternator. I threw that one in and I had no problems at first. Then I ran it on the highway lastnight and the same thing happened. This time not as bad as before. Then this morning I noticed my voltometer twitching while driving but it stopped when I was sitting at a red light. I would drive and it would twitch again. It seems like this only happens when hitting 1500 or higher RPM for a long period of time, after the alternator is wanrmed up and also when braking. Its VERY random, meaning no matter what load I put on it it randomly flickers despite the load or noload condition on the electrical system. I even tried switching to a bigger power feed wire, same problem except the volometer doesn't move around as much.

Here is what I noticed:
* Happens only when driving
* Flickers randomly despite engine RPM and load on electrical system
* Both alternators are brand new, but look slightly different from the AC Delco alternator.
* Seems to be non-existent at low speeds (and engine RPMs)
* There is one wire only in the wiring harness connected to the top on the alternator. Would this have something to do with it?
* Power wire hooked up correctly.
* When I put my stock alternator back on the problem goes away completely.

So am I getting sh*t alternators form these guys or is the 130 amps screwing with my electrical system? Is the stock PCM voltage "control" being confused or interupted by the higher output alternator?

Thanks in advance!

 

im pretty sure your pcm isn't gettin mad at you for different amperage. it sounds like the diodes and the actual power routing on the back of the alternator seems to be weird. it seems like as heat builds in the alternators electrical circuit board, it gets all twitchy. and if your voltmeter is getting twitchy then its showing that your alternator isnt charging correctly. how much did you get the alternator for? and if you could can you show a site where you got it so i could see. and does the aftermarket alternator have a different size pulley on? that would be the only reason why you would need a different belt. but if you could post the site where you got the alternators from that would be uber sweet.

 

Embarrassed to say this because I should know better.....

I purchased the alternator off of Ebay from Rare Electrical. They don't have an actual website. They have been helpful, sort of, but can not give me an answer as to why this is happening. I agree with you in that the alternator seems to get screwed upon reaching "operating temps" but that shouldn't be. Anyway it was $120 with no core charge and supposedly brand new. Another "get what you pay for" story.

Saving up and after Christmas going for AC Delco 120 AMP job.

 

what kind of vehicle are you driving?
Have you check the engine to body to battery grounds?poor grounds show there face more after you use them more.