[1project2many]

I never got back to this thread so I apologize.

I used the stock temperature sender with a resistor for my truck. It changes the scale slightly but it puts the gauge at about 3/4 when "normal." I do not have the resistance marked down so I'd have to figure it out.

It sounds like you may have a short or an issue with the gauge. The temperature sender changes resistance as it warms up. When it's cold it has 500 Ohms resistance. When hot it has 50 ohms. When the wire is disconnected the needle should be below C. When shorted the needle will go above H.

If you have an ohmmeter you can check the sender. Measure resistance with the engine cold and the gauge disconnected. Should be 500 ohms or greater. Start the engine and idle until warm. Resistance should go down to around 50 ohms or less.

If you have some resistors you could connect them between the gauge wire and ground to see how the gauge responds. Again, 500 ohms for cold and 50 for hot.

Also try moving the wire harness with the key on to see if the gauge goes to H. It might help to have a helper watching for the needle to jump around.

Edit: Is the instrument cluster powered when the key is off? Disconnecting the battery cable with key off shouldn't have affected anything.