hi all. i own a 2005 2.0ltr diesel 140bhp a4 estate.
the temp gauge only moves slightly and the heater blows cold.
i have flushed the radiator, heater matrix and replaced the thermostat but still the blower blows cold. the car has never over heated so i'm assuming the water pump is working correctly.
any help would be appriciated.

thanks again carl.

 

Isn't there a temp sensor somewhere that might be bad.

 

Not sure how different the diesels are, but in the 2.0T, your symptoms sound like either the temp sensor or thermostat. Try the temp sensor first because it's cheaper and easier to get to, but more than likely you need a thermostat. It should be throwing a code, too. P2181, I think it is. I just went through this in late 2012 and last year. Tried the sensor and that worked for a month or two and then the code came back. Ultimately, the thermostat fixed it.