Ok. I've been doing some reading and searching, and while i've found some good information, i've not heard or read about someone else having the same issue as me.

I just got my parent's 00 F150. It's a 4.2L V6 with a 5 spd. Its a 2wd.

About 2 years ago, the guages all started sweeping on initial startup. Every once in a while the speedometer would peg @ 100 mph, and then after a few minutes of driving, would go down to the correct speed. It's my understanding that this sweeping was due to low voltage conditions.

Now that I've inherited it, I've got the speedo pegged at 100, and only comes down to about 85 when you're over 35 mph. The gauge does not sweep on startup (none of the gauges do) and when you drive the truck on a longer road trip (after about 40-50 minutes of high speed highway driving) the needle will come down and read correctly. (times are not typical. sometimes it's more or less)

Is there a procedure to get the speedo to sweep manually? Could this be a case of a faulty sensor, or perhaps a bad cluster contact?

I'm just trying to keep this thing in good working order. Thanks!

-Figuarus

 

Have you had the alternator and battery tested?

 

No, but I can get it tested here soon. I'll report back.

 

Well, battery voltage was good, and alternator output was good also. 14.5v

The testing equipment i used, did say that the alt failed the diode test. Could this be the issue?

 

It's quite possible. Did you LOAD test the battery?

 

Yes, both with t he load tester and by turning everything on (lights on high, blower on high, radio, flashers, courtesy lights etc.)

 

Nothing? Anything else I need to check?

 

Have you checked the OBD2 for codes? Note - if you disconnect the battery, any stored codes will be cleared.

 

OBD scanner shows no codes, not even enhanced codes.

I did go and load test the alternator again, and this time, it showed that the Diodes passed.

 

Anyone else? I'd really rather not try to dismantle the gauge cluster if I don't have to...

Is there anything else I can test to determine a bad connector or something along those lines?