When installing the sender for your gauge onto the engine, you MUST NOT use any sealant on the threads ( i.e. teflon tape, pipe dope, RTV, etc.). Doing so will prevent the sender from making clean contact with the engine, which will result in either faulty or no operation of the gauge. The senders have a tapered pipe thread, to create a seal, preventing leakage. This pipe thread also completes the ground to the engine required for proper gauge operation