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.

 

cut your losses and go to a different shop. find a reputable and maybe even ASE certified one. even the stealership. i try and do all the work on my truck myself if i am capable. if im not i make sure im taking it to someone who is. save money and do it right the first time. im sorry this happened, but just take it to a better mechanic. anyways, voltage regulator?

 

Update. It was definately alternator. Changed it back to old one and truck ran right, no problems. It just whined. Guy tried to tell me it was PCM. I told him put another new one on it and it runs perfect now. I've dealt with them for years on starters and alternators and never a problem. The the young guy working there was installing wrong replacement. They were new alternator and not just rebuilds. Just not right one.

 

Repair shops just plain scare me. I know you have a good history with your place so they would probably take care of you. I just bought my 2005 FX4 last fall and I'm praying I don't run into one of those "parts replacement" problems. Meaning it could be this, this, or this. Lets start with this part ect. All my cars in the past 10 years have been under warranty and I get rid of them right as the warranty expires. A plus for me is I have a buddy with a full mechanic shop in his barn so hopefully he can be my backyard mechanic!! Glad you got yours fixed right!!

 

Alternator whine is quite frequently caused by a weak battery.

 

I thought battery also. Had it checked several times and always showed good. Advanced replaced battery yesturday under warranty. The manager is pretty good dude there and even upgraded to larger CCA battery. With new battery in the old alternator still whined, but charged perfectly. We even changed pulley, still whined. The new alternator is very quite and seems to be doing fine.