mazda fuel gauge problem

Most likely, it is a worn sending unit in the gas tank. The gauge works by electrical current passing through the variable resister and a float attached to the fuel pump. To replace it means removing the pump and that is done on some cars by dropping the tank. Your Mazda might have a hatch.

Sounds like a little bigger project than a average person might want to dig into. It is a old enough vehicle to have a rusted out ground for the sending unit. You could feed some volts to the gauge see if it moves if you can find the right wire to do so, if it does youll know its not the gauge. Pretty good chance you'll have to drop the tank down.

The fuel gauge, like all electrical gauges, is actually a volt meter with a different face. Power (12 VDC) is fed in one end and there is some sort of varying ground on the other lead. The varying ground is from the float in the tank or a pressure sending unit or a thermal sending unit. --- Ground the correct wire at the gas tank and the gauge should read full. -- When you fill the tank, zero the trip odo so you know how miles you have traveled.