Erratic temp gauge 164 cloverleaf 1990
My temperature gauge has become a little bit erratic. It has dropped down to a constant reading of 60ºC, rising to about 80ºC in traffic. I know what your thinking, that it's the thermostat sticking, but here's the strange thing. The fan kicks in at the 80ºC mark taking it back down to about 70º and then falling back to 60ºc when moving again. Also the gauge sometimes jerks up to 90ºC+ then jerks back to below 80ºC again, and can flick between these states as well. All this leads me to believe that it's an electrical issue rather than a sticking thermostat because:
1. if the gauge was reading accurately the fan would never switch on as it's below the 92º/97º fan switch temp.
2. the movement of the needle when it fluctuates is erratic and jerky.
Any suggestions as to how to check the electrics. I've cleaned the gauge connection at the thermostat with no change.
Thanks in advance.