Ok, my older pride and joy is giving me a weird problem. This may not be the right place to put this but there is not an electrical section to post this.

It started with my tachometer moving up and down like crazy, even though the engine RPM did not really change. I then quickly noticed my headlights and dash lights dimming and brighting. I did the usual, suspected battery then alternator. They were both bad and both have been replaced but it is still doing it.

ideas?

Thanks in advance

 

What year truck and motor are we talking about here?

And the electrical systems forum is located under "BODY". But this is an ok place to start.

 

ALIEN ABDUCTION: Remember close encounters of the third kind? Richard Dreyfus at the train tracks? I belive that was a F- series pickup too.
Something seriously sounds wrong. surging tach and headlights? never heard of that unless the frequency is off on a/c current. maybee a fried pcm
sorry to hear of your woes, and hope you get an answer soon!

 

On the newer ones, the guages will do that if the battery is bad. But, he has replaced that and the problem still percists.

 

What year CV are we talking about?

JMC

 

Three possibilities that come to mind:

1. You still have a bad alternator. This is not as far-fetched as it may seem as it is not uncommon to get a bad one off the shelf (particulalry from Auto Zone)

2. You may have a bad voltage regulator, although I think most alternators have them integrated so that replacing the alternator would also replace the voltage regulator. Not sure what your case would be.

3. Loose/bad ground connection.

... just a few thoughts.

 

Its an 88 F150.

When I got home from work today I played with it some more and got some more info. The postive terminal was cracked really bad so I replaced it. The negative is in great shape, did not make a differnce.

I have discovered that when the truck is cold it does not do it, its only after a few minutes, like 2 minutes max, it starts to do it.

 

I had the alternator checked, they said it was good. Not autozone, a local shop.

I checked the ground pretty thoroughly but I suppose I could have missed something.

 

Check the grounds from the instrument cluster. Should be inside the cab.

JMC

 

could the grounds from the instrument cluster cause the headlights/tail lightsto be dimming and what not?

It also does it only with the engine running, I moved various wires around with the engine off to see if I could find a short or something but no luck.

 

HA, it was a faulty voltage regulator inside the alternator from autozone.

Replaced it with yet another one, went with a DL this time instead of pos valuecraft.

Thanks for the tips.

 

LMFAO! Yea, if you told me in the beginning that you bought the cheapie from autozone, I would have told you to take it back and get a DURALAST. LMAO

The only parts I but at AUTOZONE is DURALAST, for that EXACT reason.

Glad you got it figured out!

Im sure you are happy with the longer warranty anyways, RIGHT? LOL