Temp gauge pegs to hot when sending unit wire is attached.
Do you mean it does that with cold engine...or are you saying it's overheating?
there is insufficient ground to make the circuit...the tester goes berserk~
There is a short to ground. Either the sender is defective or wrong for your application or there is a bare spot on the wire coming from the sender and it is touching something metal. HTH. -Jim
Looking for a Used Wrangler in your area?
CarGurus has 16,563 nationwide Wrangler listings starting at $2,990.
Search Jeep Wrangler Questions
Jeep Wrangler Experts