Nine times out of ten after I've used a car wash my dashboard temp gauge gets stuck for up to 2 hours, or until I switch off whichever comes first. Then starts working again.

Is it cos it gets wet? Will it harm it? Can I do anything to stop it --apart from avoiding car washes obviously.It doesn't happen when I drive in heavy rain.

Any comments gratefully received

Do you mean the engine temeprature gauge or the outside temperature reading in your trip computer?

If it is the outside temperature then the sensor is, I believe, behind the front bumper. Could be that it is damaged and water is getting in and causing a short when you wash the car.