coolent guage goes from hot to cold to hot to cold etc drove it with scanner hooked up and no trouble codes and two coolent temp readings one being 170and the other being 153 temp doesnt change when guage moves..

anybody know whats normal operating temp on a 99a4 1.8t auto?
thanks any help is appreciated..

thinking temp sensor maybe bad,will update..

 

dont know the exact temp but it should stay right in the middle of the gauge. you could have a faulty ect sensor or thermostat. both are cheap and easy fixes