edupin

Greetings everyone

I have an 2004 A4 Quattro with 128k miles on it. My car used to blow hot air within 10 minutes of running in really cold days.Just this winter all of a sudden it takes at least 1 hour before it begins to blow hot air not too hot either( by that time I am already at work... with froze bite on my whole body LOL)
I have check the antifreeze level and it is to the top.

The only thing that has been done to the car this year is that I've the APR Stage I installed and my AC Compressor blown and replaced.

Any comments or suggestions are really appreciated.

lyleswk

When this happened to me, it was the heater core. Flushing it did no good in my case. Ended up replacing it.

mwspera

There are several possible causes to the heating system operating poorly and not showing any error codes. The B6 needs the system to be free of air in order for the heat to work properly. That means you need to follow the procedure to bleed the air out of the system. This involves slipping back the one heater hose with the white circle on it and pressurizing the reservoir until no air comes out of the hole in that hose(only coolant).

Any leaks in the cooling system can trap air again and the system will not produce much, if any, heat (ask me how I know). The B6 has 2 notorious leaks. The infamous plastic "coolant outlet", and the o-ring in a fitting near the oil filter. Search this site for more info on these. There is a technical service bulletin on the o-ring problem.

Another big problem is the plastic water pump impellers used in these cars. These break or erode with amazing regularity.

Finally, these cars seem to be prone to cooling system scale/mineral buildup. The engineering of the heater core placement and hose routing almost guarantees the crud will end up in the heater core and stay there. Flushing the core may help but many report that the fix is temporary. The good news is that this particular model has a heater core that is easily replaced (at least it was on my '03). About $120 for a new one and about 1.5 hours to replace if you are handy.

I like to start with the least expensive repair and work up. Bleed the system and check for leaks. This is a $0 fix. Flush the system and core and re-bleed the system. Use fresh coolant. It will cost you $50-$60 but I can guarantee the coolant in your system is full of crud. Fix any leaks. Leaks cost $10-$40 for parts but the coolant outlet is a half day labor adventure to replace. Not sure if there is a test for the water pump or if there are other symptoms. Search this site and see what you come up with. If flushing works and the problem starts to return, you may have to replace the core.

Good Luck,
Mike

edupin

thank you for the comments and suggestions. I do see a small leak by the thermostat, could it be that the thermostat is not working? however the engine temp indicator goes from cold to mid range and stays there....

I need to replace the thermostat, to fix the leak. Then I will do the flushing of the whole system.... Any other suggestions DIY instructions will be appreciated!!!

Nollywood

I had a similar issue with my '01 3,0 quattro tip. In my case, my water pump was the culprit. The impellar was slipping on the shaft, and coolant flow was poor.

I replaced it, along with the thermostat and timing belt, and all was well.

j kasch

mine[a419 tdi only blows hot on the passenger side but i think this is an electrical prob? any ideas?

Nollywood

Sounds like the control flap on the driver's side isn't moving, and is stuck in the shut position.

Possibly the little servo motor has failed (never come across it happen though). More likely faulty / broken wiring, or faulty control panel.

Have you had your HVAC scanned for faults? You can also go through the actuation cycle.