i bought a 2004 audi A4 a while back. it had one issue when i bought it. its a heating problem. i wanted to get some input on this so i know where i need to go from here.

it has the dual climate control. no matter what setting it is on i can get no HOT air coming through the vents.
Although, when the car is at operating temp and the rpms are above say 2500 i can get warm air coming through the drivers side defrost vent when the heat is on high. it is only that one vent that will put out heat but it is just warm air and only when the engine is rev'd. if its at idle the vent will blow cool air again.

i know i do have warm water going through both heater core hoses as i felt them. i dunno if it might be gunked up in there? maybe some vents got stuck? im not sure.

i did do a coolant flush. before the coolant flush i had pretty much no warm air at all. after it i now have warm air in the one vent.

the car has 76k miles and just had the timing belt, thermostat, water pump replaced by and audi service shop by the previous owner.

any advise would be helpful, thanks!

 

anyone at all want to try to tackle this one for me?