Can anyone tell me what causes the Gas gauge to function improperly? It Usually sets on full untill its alomost 3/4 empty and where it lands after that one never knows.If it is bone dry it sometimes shows it.
Also I am looking for a AC compressor for my 97 SSEI.
BTW, this is Marty'* brother Mark, but you can reply to Marty.

Mine doesn't work either. I'll eventually get it fixed....I always fill up around 250 miles on the trip odo, and it takes around 14 gallons. It has an 18 gallon tank

It'* likely your sender. Mine'* been doing it for the past 40,000 miles. I'm going to be replacing the pump very soon so the problem will be resolved.

99% it would be a bad sender. That other 1% is bad wiring or ground. My bet would be a bad sender.

This is Marty talking now.

If I remember correctly in the late 90'* GM was having probs with the metal they were using for the float rod in the tank, and the chemicals in the fuel were corroding the rod, thus not allowing it to swing up/down with the fuel level.
GM supposedly corrected this sometime during 99 (my old 99 was starting to do this slightly when I sold it).

Mark or Marty, this is Mark talking now. I think there are resistors in the fuel level sensor that burn out. The best fix would be replace fuel level sensor assembly which means dropping the fuel tank as I'm sure you guys already know.

Yup, that'* what I told Mark, my brother.

Right. However, the sender is integrated into the pump, though. So changing the sensor involves changing the whole pump.

This is true.