My "new" 96 A4 has 112K on it. The AC was recharged one month ago (checked for leaks also) and the thermostat was changed at 100K, as shown by the previous owner's receipts. Yesterday I noticed that with the AC on (it was 100 outside) and in slow traffic the temp gauge rises halfway between normal and hot. The temp goes back to normal as soon as I turn the AC off. Any ideas about what could be happening? Thanks!

 

Low coolant....? That exactly what my Discovery does everytime its low on coolant.

 

Its normal.

As long as it doesn't get near the hot end of the temp guage, dont worry about it.

Check your coolant for piece of mind.

Mine does it too. I did my tbelt, changed and bled the coolant system. I am not low on coolant. When its real hot and the ac is on, guage goes to about halfway. It normally is about half of that if its a little cooler out and the ac is off.

 

Could be partially blocked thermostat, or alternatively, the electric radiator fan isn't coming on .