A6 Avant HVAC Blows Cold Air when Engine on low revs or Idle

**Jimbob21** · 11-01-2017,01:26 PM

Hi,

firstly Apologies if this has been asked before but after trolling thru endless back forum posts could not find an answer.
I am fairly new to Audi's and have had this one for only a month or so. When i first had car the heater was very intermittent, shortly afterwards it gave up completely only blowing cold air regardless of what settings were on. After extensive research and getting nowhere i took it to my local garage who bled the cooling system and re-filled using a Vac system to ensure no air locks. After that heater worked fine blowing lovely hot air etc but as soon as you drop revs down or go to idle the heat diminishes to just about nothing! I am now wondering whether this is right. Any of you out there have any suggestions as what to try next or is this just the way the HVAC works?

**zollaf** · 11-01-2017,01:29 PM

welcome to the forum. a few car details wouldnt go amiss, engine type etc, but it sounds like you might have a water pump problem.

**Jimbob21** · 11-01-2017,01:58 PM

Apologies for not giving car details etc. its a 2006 A6 Avant 2.0l Tdi S line with 90,000 miles on the clock. What is the best way to check if it is the water pump?

**zollaf** · 11-01-2017,02:00 PM

engine running, small pipe into top of coolant resevoir, should be a constant flow of coolant. if not, needs pump. when was it last changed, should have been 30 odd thousand miles ago when the belt was done ??

**Jimbob21** · 11-01-2017,02:05 PM

I dont think the pump was changed then, The belt is due to be checked before the end of Dec

**zollaf** · 11-01-2017,02:13 PM

you dont check a belt, either change it or not change it. only way to check it is to remove and inspect, and only a fool would then re fit it. best to get a new belt and pump, job done properly.. by the way, end of dec was a couple of weeks ago

**Jimbob21** · 11-01-2017,02:14 PM

I should add that the car is a lefthand drive which i brought as i spend alot of time overseas, ive driven it for 1500 miles bringing it back to UK and the temp gauge was rock steady at 90deg all the way, i would have thought that it would have had temp fluctuations during that journey if the water pump was not working

**Jimbob21** · 11-01-2017,02:20 PM

Thanks Zollaf I mistyped and didn't read before hitting post. I am going to get the belt changed before the end of Dec 2017. I will get the water pump changed at the same time. Hopefully that will solve problem.

**zollaf** · 11-01-2017,02:21 PM

you would think so but this isnt always the case. because they struggle to maintain 90 deg anyway, being efficient, they pump only needs to do very little work, which a loose impellor will do anyway, but not enough to pump coolant round the matrix. strange but thats the way it is. could also be a temp flap problem, but what you have said points to the pump. also remember that very early cars didnt have a coolant pump, relying instead on convection , heat rising, cold water falling, to promote flow through a radiator. this will happen in a modern car with a broken pump.