05 f150 with 5.4. About 6 months ago I replaced alternator with no problems. It just whinned from day 1. So, today I decided to take it back to alternator shop to check it. The guy replaced it and put new 1 on, but it was not working, said he put wrong one on. So, he changed to right one. I left happy. On way home it run same until I floored it. Then IWE's kicked in, guages quit, dash lights came on. I pulled over and it lined out, except gas guage and low fuel light on. I picked up my baby from school and went back to shop. He said it was my tensioner bad. So I go to autozone and buy and replace tensioner and Idler pulleys. I then go to advanced and have them replace battery under warranty. I pull out and floor it and it does same thing. I'm going back to shop in morning, but any help would be nice right now. I'm so pissed at myself and shop right now. Would anything else cause this? Sorry so long.

 

Stop flooring it.

 

Yelp!! That was the exact answer I was looking for. Thanks for the help.

 

bump..

 

Sounds like el dipo at alt. shop messed something up, his problem. You take it back and tell him it happened once you left his shop. If it were me I wouldn't put another dime of your own money into that issue. His problem

 

My thoughts exactly. I actually didn't have to pay anything for new alternator, he replaced it under warranty. Could he have torn something up when he put wrong one on? I put the first one on myself and never had a problem except the squeaking (whinning noise). I just figured I would have it checked while I was over in that area. It only does it under WOT. Everything works fine until WOT. You can't hear a belt slip or anything of that nature. The belt is new. Replaced it a couple weeks ago after doing plugs. My biggest concern is something burnt up in electrical.

 

I guess i would find out what "wrong" alternator they put on it. Then go to a dealership and ask them what damage that it may have done to your truck. If you haven't done so already, check battery connections, and also the alternator connections.

 

Went back this morning an changed to old alternator that whined and truck ran fine through all rpm ranges. Guy tried to tell me it was PCM. Finally got new one on and truck is doing great again. No whine with new one now. Crazy how an alternator can cause that many problems.

 

My most recent alternator experience was such that it would quit charging at 3,000 RPM's. The idiot lights would come on and the ameter would drop off until the RPM's came back down. I verified this several times to make sure. As I hardly ever pushed to 3,000 RPM, I just let it ride - took about a year for it to stop charging at 2,500 RPM. At that point I replaced it.
Don't know what the cause was - assumed it was brushes or loose bearing.