So let me get this right before I even try...(help lol)

[Xesvuli420]

Ok I'm restoring a 87 I/O Dixie Bandit, among other things I have a problem with two gauges. The trim position, and the fuel level. The fuel level started today.

To test my trim sending unit, I need to hook a voltmeter to the wire at the gauge, and to a ground, set the meter for Ohms, have someone move the lever at the unit, and if I don't get a progressive reading In the meter, either the unit, or the wire is bad. Most likely the unit.

My unit has 2 wires. I assume to carry voltage into, and out of the unit. The lever changes the resistance as it moves, and the gauge picks up the change and translates it into a "trim reading"... Correct?

To test the fuel level sending unit, I just ground a wire to the pink wire behind the gauge. If the gauge goes to full that means either the sending unit has malfunctioned, or a bad connection.. Most likely a bad unit... Correct?

Once I do these test, to confirm a faulty unit, I can run a continuity test from the sending units to the gauges, and this will 100% confirm faulty sending units... Correct?

Thanks again!

 

[Silvertip]

Re: So let me get this right before I even try...(help lol)

Lets get some terminology correct before you start.
A voltmeter is a voltmeter -- it measures voltage - not resistance (ohms).
An ohm meter measures resistance.
A multi-tester or VOM (volt-ohm-milliamp meter) is what you very likely have.
So much for details.

You NEVER attempt to measure resistance with power on (key on) or with the circuit being tested connected to other components. In the case of the fuel gauge, you have a fuel sender and the gauge in the circuit. If you attempt to measure resistance at any point in that circuit you would not get a valid reading because of the resistance of the multiple components. So here goes:

Fuel Gauge Test: Turn the key to RUN (not start). Jump the send ("S") terminal on the gauge to ground. If the gauge pegs, its good. If not -- it isn't or +12 volts or ground is missing. If the gauge is good. Turn the key off and disconnect the sender wire at the "S" terminal on the gauge. Now break out the VOM and measure the resistance on that wire to ground. If you know roughly how much fuel you have the resistance should be somewhere between 30 - 240 ohms with 1/2 full being about 100 - 109 ohms. If that measurement is ok then the system should work. If not, verify the ground connection (as in disconnect and clean it) at the tank sending unit. If the measurement is not within the range indicated, remove the sender and test it by repeating the procedure measuring directly at the sender and moving the float arm up and down. A bad sender will not show resistance in the range indicated. To test the trim system, the gauge check is the same. To test the sender (two wire) disconnect one of the two wires and measure across the sender. Failure to show varying resistance = bad sender.

Here is a diagram of the fuel gauge circuit.