Mine was the wire from the switch. It was rubbing on the fan belt and burned right through it. I read a post from someone who said to check 6-8 inches from the switch. He was spot on. Disconnect the wire going to the sender, disconnect the other wire beside it. Pull the harness up toward the top and examine the harness for damage. Mine had a hole burned through it and the wire was broken. I repaired it and carefully fed it back down making sure to zip tie it away from the fan belt. Now my gauge works.