2000 Dash

[makoman]

Gas gauge and temp not working on my 75 2000. Two warning lights and tach are working. Unscrewed it, found a mess. After cleaning out the mouse house, found temp wire, gas wire and black ground wire all disconnected. Reconnected, nothing. Both gas and temp meters pinned left. Checked for broken wires, none. Checked voltage stabilizer, 12 volts coming out. I know its should be less. Going to replace it. Question is, since gas and temp gauges are getting full 12 volts, shouldn't that move the gauges, or even pin them the other way?
Thanks for the help.

 

[sumbeam]

Ground the wires that go to the censers they should move.

 

[Mark Slater]

Double check that the black wire is connected, both ends. Look past the mouse house you found. Not sure of the 2000 wiring colors or where they go. A lot of these have been hacked so bad the wires change color three / four times before they connect to something.
On neg ground systems with single wire sensors, if you ground any of the sensor wires the indicator will light or gauge will pin.

 

[Sean in PA]

Could also be the voltage stabilizer itself is bad, as the temp and fuel gauges are both powered by the stabilizer, while the warning lamps for the fuel pressure and charging circuit are powered from incoming voltage from the key switch before the stabilizer.

 

[makoman]

OK, grounded the gas gauge and temp gauge, both gauges moved. So just ordered stabilizer. Hope that does the trick.

 

[Sean in PA]

If the gauges moved when you grounded them then the stabilizer is probably good. The stabilizer just provides a lower average voltage to the gauges than the full 12 volts, and having the gauges move when you ground the other side of them shows that the stabilize is providing power to the gauges.

The side of the gauges that you grounded normally connect to the "senders" for their respective functions. The fuel gauge connects to the fuel level "sender" and the temperature gauge connects to the temperature "sender". The "Senders" are really just variable resistances that vary their value of resistance as the condition that they are monitoring change. The fuel "sender' varies its resistance as the float on the arm inside the tank goes up and down with the level of the fuel. The "sender" for the temperature varies its resistance as the temperature of the coolant surrounding the "sender" in the head changes. The other side of both "senders" connects to ground, so they ar varying the amount of resistance between the gauges and ground.

After the grounding test showed that the gauges themselves and the voltage stabilizer are good, I would perform a similar grounding test on the far end of the wires that go to the senders by grounding the far ends of them, and if the gauges move then, the senders both have a problem, and if the gauges don't move, then the wires have a problem.