Need temp sender (gauge) help

First, I have used the search. So I just did the head gasket on my 96 4.0 manual trans 4x4. Now my temp gauge pegs as soon as the ign is on, cold engine. Ive grounded the wire and the gauge responds correctly. When I plug the sender into the wire, but not threaded into the block the gauge reads correctly=cold. As soon as the sender touches the block it pegs the gauge. So Im getting a ground out condition when the sender touches the block?! My ground strap, right next to the sender, is tight. Im sure this is simple but what am I missing? Thanks!

The sender provides resistance to a coil in the gauge, which produces a magnetic field that pulls on the gauge needle. As the resistance varies, the amount of current flowing into the coil varies, which produces varying levels of magnetism. With the sender wire disconnected (infinite resistance) the gauge should go to bottom position, with sender wire directly grounded (no resistance) the gauge should go to highest position.

It sounds like you have a bad sender that is grounding out internally

ehall said:

The sender provides resistance to a coil in the gauge, which produces a magnetic field that pulls on the gauge needle. As the resistance varies, the amount of current flowing into the coil varies, which produces varying levels of magnetism. With the sender wire disconnected (infinite resistance) the gauge should go to bottom position, with sender wire directly grounded (no resistance) the gauge should go to highest position.

It sounds like you have a bad sender that is grounding out internally

Click to expand...

x2, replace the sender.