I'm having trouble with my fuel gauge. I ohm all my wires and everything is good. I made sure my sending units ground is good. I ohm my fuel gauge and I get 13.4ohms with my gauge set to 200ohms (with the cluster unplugged). When I plug my gauge cluster in and turn the key on I check the black wire (at the plug) that feeds power to the resistor? of my fuel gauge and oil temp and my meter bounces between 12v and 10v. When I unplug the cluster and check the black wire (at the plug) I get 12v steady. I have two gauge clusters and when I plug the second one in I get the same bounce in voltage. Is this normal?

Thanks for the help

 

Does the gauge go all the way to full when you ground the sending unit wire?

 

No, I tried that and I would think it should. But I use a test light on the back of the gauge and the needle slowly goes up to full.

 

I'm guessing the test light gives enough resistance through the bulb to make the gauge work. But why is the sending unit not doing it??? Some times electric stuff drives me nuts!! You would think it would be like math, there is always a correct answer. Just finding it, like with math, can be a little nerve racking. :P

 

We need to start over. The test light business is not correct. When you do the ground test, you should unplug the bullet connector of the sending unit, and ground the harness-end of the connector to the screw that holds down the sending unit ground ring terminal to the crossmember. This should be done with the key on. The fuel gauge should peg full. Are you doing it this way?

 

Yea I grounded the sending unit wire, and the gauge does not mover.

 

The gauge should peg "full" when you ground the sending unit wire to ground.

The sending unit also opperates under a pulsed 5 volt feed and not a straight 12 volts.

The ohms for the sending unit (not the gauge) should more or less be in the range of approximately 8-12 ohms full and 70-73 ohms empty.

Josh

 

So is that what that resistor (or what ever that thing is called) on the back of the cluster suppose to do?

Thanks
Aero

 

Is there any way of testing that resistor?

 

i believe to test it correctly you would have to scope it

 

What resistor are you talking about?

Resistors don't get scoped. Oscilloscopes are for measuring time-variant voltage waveforms.

 

right i thought the thing on the back of the gauge sends a voltage wave signal.

that would be what hes calling a resistor

 

The "thing" on the back of the cluster is the Instrument Voltage Regulator.

Josh

 

Ah, okay, that makes sense. Yes, the voltage regulator does send out a pulsed waveform. When he said resistor, I thought maybe he meant the ALT light shunt.

 

lol sorry for the misinformation, I did post that I wasn't sure what it was called. So can I check this with a normal voltmeter?

Thanks for all the help guys!!!