It’s cold outside and I have no heat even the temperature is set to HI. As I’m going through the temperature setting, I can hear the inside vents flaps are switching and the fan changes its speeds, this shows that the main controller is working. After reading and getting suggestions from many Audi enthusiasts in the Audiworld.com, I found the problem. 1. Check if the heater valve is working. The heater valve is the one that let the hot coolant from the engine to the heater core inside the car so the fan can blow hot air to inside of the car (then you have heat). This valve is vacuum operated which is different from Honda cars, a cable pulling it on/off (close/open) from the lever in the driver’s front panel. In order to see all these components, we need to remove covers if your car’s still very original.
After removing this cover, you should be able to see the heater valve.
On my car, it was out (pushed out) which is opened and I could feel the hot coolant on both inside and outside the valve, input/output hoses. So the heater core should have hot coolant going through it, but I check the valve anyhow. Turn the temperature to “LO” setting and the valve is still opened. Following the vacuum line and I found out the main vacuum hose was broken at the engine intake manifold.
It’s so hard to see the connection and especially after getting some new hose to replace it. It’s so tight under all those hoses. I had to move the intake cover out a little to get my hand under there.YES, the hose FIXED the heater valve problem, I can see the valve pulled up (close) @ “LO” setting and pushed out (open) @ “HI”. OK, but the heat is still NOT coming out of the vent.2. Check the HEAT/AC vent flap. Go to the other side (passenger side) and look at the flap linkage to see if it changes its position with “HI” and “LO” settings.
Mine was at this default position which is HEAT OFF/ AC ON. I try to push the linkage forward to heat, but it’s locked tight due to the control flap valve on the other side. Changing the temperature, with AC on, this flap sits still, DEAD. Since it’s locked at the NO HEAT position, we have to go to the other side to get into the flap controller. To remove this controller, we need to remove more stuffs.
To get to these screws and remove this cover, we need to remove windshield wipers and its whole linkage. A little more work. We need some allen wrench (hex) and 10mm sockets or wrench. I forgot the size of the hex wrench 6-7mm?
Remove the metal wiper cover after 4 hex screws and wiper arms removed.Then remove the plastic cover.
To get to the wiper motor and linkage, remove all brackets. 3 10mm screws on the motor bracket.
3- 10mm screws on the linkage.
After 6 10mm screws are out, we can lift the whole linkage out to the side so we can access to the screws of the flap controller.
Now we can check if the flap linkage is broken of have kinks somewhere, but they do look intact to me. We’re pretty sure that the servo unit is broken because we didn’t see any movement on the other side linkage. Anyhow, we still turn the temperature to “HI” and “LO” to see if the flap linkage is moving, but it’s dead still in my case. We don’t have a new flap controller motor, it’s the winter and we need heat, therefore, we must remove the flap motor and set the flap linkage manually to heat position. Use a philip head screw driver to remove the screw of the linkage and pull out the motor and linkage. When the motor and the linkage is out, then we can go to the other side to flip the flap from HEAT OFF to HEAT ON.
Turn the temp to “HI” with this position, and the car is filled with heat from the vent. It’s a wonderful warm/hot feelings… hahaha. No mystery anymore. I didn’t have time to fix the servo, but all I care is the heat and AC on max. I took open the motor to see what’s inside.
There is a write up on how to fix the servo unit very clearly on audiworld, if we need to fix it when we have time, we can down load the pdf file.Re-set the linkage on the flap motor to HEAT ON position, put back the philip screws, put everything back: covers, wipers.SO, with this configuration, we still have AC/HEAT whenever we want. The only thing that we don’t have is the smoothness of the temperature. We don’t have the air of 70,75,80. We will either have extreme heat or extreme cold. The AC will still blow cold air when the heater valve is closed and the heater core is cooled down. I tried both conditions and they work.When I have time, I’ll follow the instruction of the pdf file to fix the servo unit.Some great threads on Audiworld.Austinado16There are many troubleshooting techniques about heat/ac problems in Audiworld.com. To me, always try the simple things first. Some people jump straight to the part that seldom fails like bad heater core (big job), just like when the car doesn’t start, the fuel filter or air filter are clogged (these have never happened in my entire life owning old cars).Now we have heat predictably in the winter and AC in the summer.