2004 f-150 2wd 5.4 Whenever i am getting into the throttle a little bit and the rpms are starting to rise my headlights go dim rpms start to fade like i am losing power and i sometimes here a squeak. Belt slipping?

 

Never heard of something like this before, but here's my best guess:

I think your alternator is going bad. When your RPMs increase, your alternator is driven faster as well. Slipping belt may mean your alternator pully is starting to slip, which means either

1. bad belt
2. bad tensioner or
3. bad alternator.

My guess is alternator...but maybe someone who knows what they are talking about will give it a shot!

 

Thank you i will check that out

 

Altenator checked out ok today. Leaning toward the belt ?

 

It's possible, how many miles are on it? How's the belt tension? Is it tight? Shouldn't be much free play there.

If the belt has the proper tension, I'd start by replacing it. Something's causing it to slip when you get on the throttle. When the belt slips, your alternator likely stops spinning, which would explain your lights dimming....

Let us know how it goes...

 

Hey 001 thanks again i have 125,000 on the truck belt seems tight. Is the tensioner adj ? Priced a belt at the local auto parts store $30. Hard to replace ?

 

I've never seen an adjustable automatic belt tensioner before, but I guess it's possible.

Disclaimer: I have NEVER done a belt on one of these trucks before!!!

If it's like every other vehicle I've done with an auto belt tensioner, this is how you do it: You find the tensioner, which most of the time is a spring loaded arm with a pully at the end, which puts pressure on the belt. Many auto parts stores make a "serpentine belt tool" to help with this, but often a simple wrench will do. You have to get down there with a wrench and rotate the arm away from the belt, releasing tension on the belt. At the same time, with your other hand, you slip the belt off of one of the pullies, and remove the belt.

Thanks to Tylus, I am soon going to have the service manual again, but that 7 gig download will take me awhile...so this is the best I can do for the moment....

If you have trouble, post some pics, and I should be able to assist further...good luck!

 

001 your guess turned out to be correct, it was the altenator. Replaced the belt to. Thanks again.

 

Thanks for letting us know how it went; glad it worked out for you!