cheesypoof

I have a 2001 A4 1.8TQ with no heat.

The heater core is not plugged. I unhooked the outlet hose, and started the engine. Coolant was flowing out of the hose. The coolant flowing out did not seem to have a lot of pressure, but I am guessing that it is normal. Both hoses also seem to get hot after the car warms up.

The climate control system is not showing any fault codes (using the climate control buttons to display the diagnostics screen)

When I look under the dash from the passengers side, it looks like the levers for the control flaps are moving when I change the climate control temperature.

The engine temperature is rock solid at half way between H and C.

I suspect that the problem is one of the air control flaps under the dash, but I also thought that the climate control self diagnostics would show a fault code if one of the flaps failed to move.


What else should I check?

ezveedub

Could be the heater core itself. It's been known to get plugged up and produce little or no heat unless the engine is revved. See if you feel any warmth on the HVAC box itself under the dash. If its hot where the heater core is, then maybe you could have a flap issue. Also, some people reverse the heater core hoses to see if it produces any heat. If so, you have a partially plugged heater core and some of the debris has flowed back out when the hoses are reversed.

4Driver4

First flush the core and bleed the system thoroughly. If still no heat, do some testing with VAG-COM

cheesypoof

The problem was air in the cooling system. I bled the system and now I am toasty warm. Amazing that a little bit of air in the line can make the difference between ice cold and blazing inferno.

ezveedub

That's usually because the heater lines are at the highest point in the car, so air gets trapped there. That's why they made a bleed hole in the heater hose and also state to fill the coolant tank with an extended tube installed. With some shops, they don't have this issue anymore, because they fill the system with a vacuum filler. Not expecting owners to have these, but they work great. Glad to hear your heater is now fully toasty and warm!

jimrobertson

When bleeding the heater core it is essential to let the engine come up to 90C. When bleeding the core rev the engine to about 2200 RPM with the heat temp set at maximum. Keep bleeding the heater core until there is a steady steam of ATF out of the bleed hole that goes about 2 feet high when rev's are at 2200RPM. When this is happens it likely means all the air is out of the system. Then there will be heat.

4Driver4

I bleed it cold using compressed air. Much better result.

turbo510

There's not much to gain by setting the temp to max as these cars don't have a heater valve for the coolant. Coolant will flow through the core the same no matter what the temp is set for.

Prospeeder

I see this alot, the core is just bad. If you ever cut one open you see why. They will flow fine, but its because the water just goes in and then right back out the easiest path. even if 90% of its clogged, its just runs right through that other 10% and there is no heat. Because of the core design, its a waste of time to try flushing. Its yet to ever work for any cars that have came through my shop.

sdmags

I have the same car same problem. What's the proper way to bleed the system? Pictures would be very helpful.