Travise90

Hello all, I have a 2006 F150 5.4l with 228k on it. About 10,000 miles ago I had my alternator go out on me at about 10 pm 2hrs away from the house. Luckily my battery lasted me long enough to pull off freeway and into a autozone which luckily was open. Switched out old for new and I was on my way again. My problem is that when driving at a constant speed my voltage spikes for about 5 seconds and goes back to normal. It spikes to about 15.9 v. It also makes a horrible grinding noise while spiking. I have a new battery as well. This has only happened about 6 times. Anybody have any ideas as what could be causing this. Thank you

BadFish523

Voltage regulator in a cheap aftermarket alternator.

BadFish523

These trucks are picky about alternators. In your situation you didn't have much choice though.

Travise90

Yea I didn't have a choice. Had my girlfriend her nephew and 2 dogs in the truck. So I had to get a cheap duracrap one. And I've tried talking to autozone and they say if it checks out fine they won't replace it or give money back. But I may just bite the bullet and get a motor craft and just eat $250 for the other one. Would rather do that than fry something.

BadFish523

Just tell them its spiking in voltage and you think it has a bad voltage regulator. See what they can do from there?

Travise90

Yea I guess I'll try that. See what happens. Thanks