So had to replace the sending unit on my aftermarket electric temp. gauge and now it will work fine for a sec or two then jump to max. I thought there might be some interference as it seems to do it once I rev up for the first time but sometimes it just maxes out right when I turn on the switch before I even start the car. So maybe the sending unit is bad? I was wondering if you get air in the system by changing the sending unit while full and if that would mess it up. I may just go to a mechanical if it is interference.