What should the voltage guage read - 1997 Saab 9000

the voltage in use is dc volts so your problem indicates that the wires are connected with the wrong polarity
try switching the wires over

voltage gauges read the out put voltage from a alternator
it should be a max of 14.5 to 14.8 volts
if it is higher then the alternator or regulator is faulty and needs removing for a bench test or replacement
there may be a connection to the dash light through the light control module that controls the voltage to those lights
fix one and see it that fixes the second.

may be a bad float or the connection to that float is broken

lamp burned out, ?
but does the fuel guage work 100%
and at what tank level do you expect the lamp to come on.?
did you read the FSM on this, its covered
or alldata.com?
free.
http://www.jeep4x4center.com/knowledge-base/index.htm?utm_source=cj#service

on this car, the PCM reads the fuel level then sets the fuel guage
and if the level (voltage from tank sender) is below a specific
voltage , it glows the lamp, low fuel
so if the fuel guage works, and the lamp is dead, the lamp is burned out. (or conn. bad to it)

Hi, The Sending UnitThe sending unit is located in the fuel tank of the car. It consists of a float, usually made of foam, connected to a thin, metal rod. The end of the rod is mounted to a variable resistor. A resistor is an electrical device that resists the flow of electricity. The more resistance there is, the less current will flow. In a fuel tank, the variable resistor consists of a strip of resistive material connected on one side to the ground. A wiper connected to the gauge slides along this strip of material, conducting the current from the gauge to the resistor. If the wiper is close to the grounded side of the strip, there is less resistive material in the path of the current, so the resistance is small. If the wiper is at the other end of the strip, there is more resistive material in the current's path, so the resistance is large.First of all, the guage needs a 12 volt electrical supply to operate. The entire system extends from the fuse block inside the front passenger compartment, through a resister (which lowers the voltage), on to the float assembly inside the gas tank then on back to the fuel guage itself,

First , test the fuse responsible for the fuel guage. Note: this fuse is usualy responsible for the fuel guage only or several items.

If the fuse checks OK, then a check must be made to troubleshoot the entire length of the system or until the problem is located.

If the fuel tank sending unit is faulty, the fuel guage can read any position, including full or empty. The sending unit can be tested by first checking to see if the unit can be removed from the fuel ttank by either partially or fully lowering the tank.

Prior to removing the sending unit, check to ensure there is voltage at the wires leading into the fuel tank.

With voltage confirmed, remove the unit and check for continuity at each end of the float arms travel .with a multimeter If the unit does not check good, replace the unit. Note: Sometimes after a long time in service the strip of resistive material can wear through and plainly be seen.

If the unit checks good, there could be a bad ground somewhere along the line.

If all else checks good, then the fault most likely is a bad fuel guage. The guage also can be tested by applying varying degrees of voltage (0-12VDC ONLY) to the teminals at the rear of the guage.

If the guage is bad, it must be replaced.

I hope this information has been of assisstance to you,
Randy Atchley



First of all, the guage needs a 12 volt electrical supply to operate. The entire system extends from the fuse block inside the front passenger compartment, through a resister (which lowers the voltage), on to the float assembly inside the gas tank then on back to the fuel guage itself,

First , check test the fuse responsible for the fuel guage. Note: this fuse is usualy responsible for the fuel guage only or several items.

If the fuse checks OK, then a check must be made to troubleshoot the entire length of the system or until the problem is located.

If the fuel tank float sending unit is faulty, the fuel guage can read any position, including full or empty.

If the wiring is all good

To confirm if the fault is with the Rheostat float within the fuel tank or the fuel guage in the dashbboard, you can remove the wiring to the fuel tank float. If the guage reading changes- to full- then the guage is good and the fault can be a jammed rheostat which can be removed from the tank and replaced after draining the tank. The guage can be tested on the outside with a ground wiring to the plate of the fittings and as the float is moved the guage must show a change in reading. if not the voltage must be measured to confirm the working of the guage.

could be the guage itself, the sending unit for those guages or the wiring in between. find the sending unit, should be two wires the sending unit actually changes the amount of voltage going to the guage. cross the two wires over at the sending unit, the guage should read all the way in one direction, do this for both guages. if the guage moves to an extreme position when the wires are crossed the guage and wiring are fine and the sending unit is the culprit. if you cant get the guages to move by crosing the wires, suspect the guage itself. find you a freindly garage to help w your repair. hope this is useful

Thanks for choosing FixYa and welcome. You may have a bad sending unit. It could also be a defective dash voltage regulator, lost ground at sending unit, break in the wire at the dash harness too. It can be anyone of these to be honest.

Check the voltage with the engine running. If it is 14.5 to 12 it's the guage. 14.5 and above it's the regulator.

When testing a fuel guage you should disconnect the wires to it,guage should read over full,ground the float wire,turn off key then turn back on should read empty.You have to cycle the key for guage to move.If still inop the wire is broken in the harness between the tank and the dash.Voltage on the float wire is low.When tested with a test light it will barely light the light and pulsate.This test indicates the wiring is good.