Here are some kinda weird fact:

When i had my 4.11 gear everything was fine,my voltage gauge was at the 3\4 of the gauge(around 14.5 and maybe a little higher).

I then change to 3.90 and reprogrammed the pcm with the new scalar.Since then my voltage gauge only go to just a little over 1\2(seems to me like 13.50v or a little lower) and after a while it would get right on the center of the gauge(13.00 or a little higher).

I took a volt meter a checked the voltage on the battery at idle.Even with the low reading of the cluster gauge i still got 14.60 volts at the battery so the alternator is still working perfectly(new from last year).

So is there anything that i could check or this is just my cluster that is getting old...

 

The volt gauge has no interface with the computer. Voltage come through the ignition switch to the cluster. Check other switched power circuits at the fuse box and see if they all read the same. Normally, the non-switched sources read a little higher.

 

Interesting fact.

-When the car warm up the alternator gauge cluster needle that was showing 14.5v would lean toward the center of the gauge(13 volts).

-With the flasher (left or right) engage i can see the needle kinda follow the flasher clic and move down each time that my flash clic.

-If im running lower than 2000rpm in every gear the gauge show a little over 13.50 but when i pass the 2000rpm i would get 13.00.So when i go WOT the neeedle go under 13volts.

If im at idle and and i put my headlight ON...The gauge rise automaticly to 14.5 volts.

Does this give you any idea of a commun problem or i just leave it like this.

Thanks again

 

The alternator puts out higher voltage when the battery needs it. Example after starting the battery is slightly drained and the alternator voltage will go up higher 14.4 to recharge the battery and then slowly drop back down. When running along without a load and the battery is fully charged up the regulator will sense this and reduce the alternator output to lower voltages 13.0 and just trickle charge the battery to prevent overcharging (boiling off the battery fluid). When you put on the headlights the batter voltage drops due to the load requirement and the regulator cranks up the alternator voltage to replenish the battery. What you are seeing looks normal. As Rob stated in post #2 the PCM has absolutely nothing to do with the alternator output voltage, the voltage regulator internally installed in the alternator manages the alternator voltage output.

 

This actually happened to me only one time in all the years, I uploaded a tune to a customers 02 T/A, after the upload his guages were all screwy, tach was not reading right, temp guage, fuel ect. I thought no way is it connected to the pcm tuning, well I uploaded his stock tune and all guages went back to normal so go figure???