Heat control problem,ac works sometimes

sosounds like you should be chkg all your fuses in the fuse box. It only takes one to do this as they are often interconnected. cheers

Make sure the blend door flap is traveling all the way to the open position when sliding dash control to heat position.

There is a heater core valve on vehicles that have a dual zone, ( climate control ) systems. The valve is in the area of the heater core.

Something to try. allow the engine to run for 6 to 8 minutes with the heater wide open, then, turn the engine off and reach back and feel the 2 hoses at the firewall that lead to the heater core. If only 1 is hot you do have some blockage, if both are hot then it is circulating properly and your problem lies somewhere else.

Dual zone systems also have a split door between the heater core and a/c evaporator that often stops functioning properly and it can block the hot air comming from the core.

I had no heat after replacing the water pump on my 96 Audi A6 quattro. After reading the last post, I found a bleeder on one of the hoses going to the heater core. I just turned it and it allowed the air to escape. Then I had heat.

system may be blocked check for any restrictions in system

put a clamp on the heater hoses ,expensive repair i think ,,possible climatic control computer

my audi a6 2.8 i need radio cod

another difficult one to diagnose without car in front of me iam afraid ,could be anything from a head gasket to a partially blocked rad caused by no ANTIFREEZE ,try it again and turn the heater on max heat and fan on max and see if runs hot then if its ok ,let engine cool and put about 200grms of caustic soda in rad and run it for half hour ,let it cool and flush out the system with a hose pipe .then refill with water and try another drive ,if its ok then refill with antifreeze ,if its not try the caustic again .if that doesnt work trade it in quick

if its a climatronic head unit and there is a fault the head unit sometimes flashes to tell you there is a fault,diagnostic equipment should be able to pin point your problem