bcrump5252 said:
the only gauge I can think of is the fuel gauge, becase i ground it then hook the sender wire to it and then hook a 12v source to it, so wouldnt that be to much voltage for the sending units?
You better not be putting a 12V feed to the sender, you will fry it. The gauge should have a wire on it for the sender. It will have some voltage coming out of it. Don't know how much, I didn't design the thing. The sending unit is a varible load on that sender wire. There is a pull up resistor inside the gauge (not that you need to worry about). Depending on the resistance of the pull up resistor, and the resistance of the sending unit there is a direct corolation to the voltage in between the two. That voltage is what the gauge reads and is calibrated in E to F.
Take an ohm meter and measure the resistance of the sender wire to ground. it should be between 10 and 70 ohm (not k-ohm or m-ohm). If you get that your sender should be good.
Next take the gauge. Hook up power and ground. Take the sender wire and touch it to ground. when you touch it toground the gauge should peg at full. If you happen to have a few spare resitors in the 10 to 70 ohm range laying around, try grounding the gauge sender wire through the resistor. Get different gas gauge readings. Now hook the gauge to the sender and you will have a working gas gauge.
Note that all grounds must be common. testing the gauge with a battery on the ground won't do anything with the sending unit in the truck unless that test battery and the truck have the same ground.