If its not a hot day then yes I can drive it around even with the interior heater switched off because there is enough air cooling going on as I drive. If I then place a demand on the system like air con, or heavy traffic, it starts to get too hot on the temp gauge on the dash. On an average day I like the interior reasonably warm and cosy so the heater is on - in this scenario, the temp gauge never goes above half way even in traffic. The air con stays really cold though when I do try to use it regardless of the engine runing hot, so that's got me a little stumped as I'd have thought air con wouldn't work properly if the rad fans are not spinning. My temp gauge appears to work normally (I've known/owned the car for several years) and I had ordered a temp sensor just in case, but wondered if there was test I could perform on the original sensor first (like has been mentioned above). Will have to try that. I remember years ago just earthing the temp sender unit on a car and watching the gauge got to max in order to test it, but I'm not having any issues with accuracy at the gauge unfortunately. I'll have to try the 12v power test directly at the fans and see what's what with that. I'm hoping the ECU isn't playing up....