Good morning. I am trying to get a temperature gauge working on the ex-turbo car that now has a stock 2.0 L engine in it. When I wire the gauge up to the electrical system as soon as I turn the ignition on it pegs full hot. I tried a second gauge as a sandwich check in it behave the same way so I don’t think it’s a gauge issue but something else is wrong.

I have power and ground to the right place on the gauge, so my guesses center but what would cause that? Sender not being grounded? Maybe just a bad sender?

Thanks!

possibly a sensor short circuit, or in the wiring.

Sender is grounded to case via mount. Single wire runs to gauge. You can test the wire from the console harness to the plug just beneath battery. My guess is wire is grounded out in one of the engine case wire holders

Just went through this. If you shorted + to the ground side of the gauge or the sender, the sender is fried. Disconnect the sender wire and see if the gauge does not peg when the key is turned. My sender was 30 years old and finally gave up the ghost. Replaced it and all is well now. You do need to make sure the sender is grounded, not just floating around or in a bracket that does not have a connection to ground. If you have it on a rubber extender hose, that does not provide ground.

Does the sender have an ohms value?

Does the signal wire run thru the stock location? Behind the front fan shroud?

Good morning, thanks for all of the responses.

I just checked and when I connect disconnect the temp sender lead but then apply 12v power and ground the gauge pegs. Bad gauge?

If you apply 12V to the gauge without the sender, then the needle pegs; that is normal.
If there is a short in the sender or wiring, then you get the same thing. The gauge is working fine still. You need to replace the sender or fix the wiring. If you place a 10Kohm resister between the wire and sensor at the sensor, and the reading changes, then the sensor is at fault. If nothing changes then the wiring is at fault.

Thanks - I just ran a new wire directly to the gauge and same thing happen (gauge pegs full hot) so seems like I have a sender issue.

Thanks - I just ran a new wire directly to the gauge and same thing happen (gauge pegs full hot) so seems like I have a sender issue.

If the sensor and wire represent a low resistance to ground, the gauge will peg. Open circuit (high resistance) will not move the needle.

If you disconnect the sensor wire at the gauge, how much resistance to ground do you measure?

If you disconnect the sensor wire at the sensor and disconnect the wire at the gauge, how much resistance to ground of the wire do you measure? This will test if the wire is shorted somewhere.

My car did this when I smashed the wire between the motor mount bracket and motor mount bar once. I replaced the wire, and it worked again.

--DD