[davepl]

Depends on where the gauge is getting the erroneous ground signal from. If you're certain its not from the sender, then it's in the cluster or the gauge.

I don't know what the resistance is on the idiot light senders, but it should be high enough I think that it shouldn't cause this even if you had the wrong sender.

What I did was boil mine in a pot of water with a thermometer and an ohmmeter, wrote down the readings of resistance v temp, and mapped it out. So I know mine's right, and you can't go wrong doing it that way...