i have the summit brand setup in my mav the problem is the water temp will work then it will go up to 320 degrees untill i rev the motor up then it will tell the real temp it does this at any temperature of the motor i tought it was a ground issue so i ran a ground and touched it to the sending unit and that didn't help and i have 2 grounds from the motor (one to the side of the engine bay and one that goes to the battery then to the core support all grounds are clean (i just did them ) and the oil pressure gauge and volt gauge work fine
Check to see what the voltage output of the Alt is when the gauge goes up to 320. Then check it again after you rev the engine up. Kinda sounds like the Alt isn't kicking in and charging untill you rev the engine up. 1 wire Alts do this, Just a thought.
