Living Dissed

The Climate Control head controls five servos (four electric and one vacuum), and a fan motor, in a box containing the air conditioning (A/C) condensor and heater core. The heater core continually receives hot water from the back of the engine. There is no flow control valve - the core is always hot. The head controls heat by moving a flap to regulate the amount of air passsing through the core. The head controls the A/C compressor clutch through one wire, which goes through a series (pun intended) of circuits, finally ending up at the compressor clutch.

Living Dissed

1. Out of sight, by the driver's throttle foot, is an electrically-controlled servo (red) which the control head moves to three positions:
- a) the defrost vents
- b) a 50/50 blend between the defrost and footwell vents
- c) the footwell vents.

2. To the right: Centered over the central tunnel, screwed into the bottom of the climate-control box, are two electrically-controlled servos. The servo closest to the firewall (natural) controls the amount of air shunted from the A/C core, through the heater core, then blended back into the main air stream.

3. Moving from the firewall towards the shift stick is a second flap-controlling servo (blue). The head rests this flap in three positions:
- a) middle vents
- b) a 50/50 blend between the middle vents and the defrost/footwell flap
- c) the defrost/footwell flap.

4. Inside the climate control box, centered over the central tunnel against the firewall, is the hot-water heater core. There is no water flow control valve - this core continuously receives hot water from the heads of the engine. It gets cold in Deutschland, and Audi's engineers made a robust heater system.

5. Directly above the passenger's left foot, is the body of the climate-control box containing the A/C condensor.

6. Slightly to the left of the passenger's right foot, is the continuously-variable squirrel-cage blower fan.

7. Directly above the fan is the fan's controller. The controller has a large metal heatsink protruding into the box's airflow.

8. Directly above the passenger's right foot, is the vacuum-driven servo to open and allow cabin air to recirculate into the system.

9. Out of sight, at the end of the dashboard, in the extreme upper right, just below where the A-pillar protrudes from the dash, an electrically-controlled servo (black) operates a flap to allow outside air to enter the system.

Living Dissed

1. In the gap between the windshield and hood, on the passenger side, is an opening allowing fresh air to enter. There is a replaceable cabin air filter over this opening.

2. At the base of the passenger's a-pillar, an electrically-controlled servo (black) operates a flap allowing outside air to enter the system.

3. A vacuum-driven servo can open to allow cabin air to replace the fresh air.

4. A continuously variable speed squirrel-cage blower fan.

5. Above the passenger's left foot is the A/C condensor.

6. An electrically-controlled servo (natural) operates a flap regulating the amount of air shunted through the heater core.

7. An electrically-controlled servo (blue) operates a flap behind the radio. The control head moves this flap to three positions:
- a) middle vents
- b) a 50/50 blend between the middle vents and the defrost/footwell flap
- c) the defrost/footwell flap.

8. By the throttle petal, an electrically-controlled servo (red) operates a flap which the head rests in three positions:
- a) the defrost vents
- b) a 50/50 blend between the defrost and footwell vents
- c) the footwell vents.

GBW

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2783193.phtml">Link....</a></li></ul>

Pscheoverdrive

<a href="https://forums.audiworld.com/a4/msgs/2806326.phtml">Have fun with this one...</a>

BSK

link contains a post to a company that will replace with your core return for less than 100$<ul><li><a href="https://forums.audiworld.com/s4/msgs/2801508.phtml">https://forums.audiworld.com/s4/msgs/2801508.phtml</a</li></ul>

BSK

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2766643.phtml">https://forums.audiworld.com/a4/msgs/2766643.phtml</a</li></ul>

Nate (ETKA+Scumbag)

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2813071.phtml">https://forums.audiworld.com/a4/msgs/2813071.phtml</a</li></ul>

wiinky

Finally extinguished the CEL caused by "Secondary Air, incorrect flow". The vac line from the secondary air injection solenoid valve going to the left (driver side) Combi valve was pinched. ( see Bentley A4 Manual pg. L24-20, picture A10-0277). That brassy hole receives a bolt that fastens a small, rectangular platform (securing plate) that has several vacuum related gizmos attached to it. It's located just rear of the intake manifold. "Somebody" ran the line under the platform and then pinched the line when tightening the bolt. Over time, heat did the rest. Mr Squirrel told me exactly where to look, otherwise I never would have found it.

I cut out the sqwashed section, spliced it with the smallest diameter vac line from NAPA, cleared the code with Vag-Com and then me &amp; Rocky did a Victory lap around the neighborhood.

<img src="http://pictureposter.audiworld.com/102137/far.jpg">

<img src="http://pictureposter.audiworld.com/102137/close.jpg"><ul><li><a href="https://forums.audiworld.com/a4/msgs/2423308.phtml">Definitive guide to fixing secondary air injection incorrect flow detected problems.</a></li></ul>

BSK

Complements of the S4 and Allroad forums:<ul><li><a href="https://forums.audiworld.com/s4/msgs/2520989.phtml">How to repair pitted and hazy headlights.</a></li></ul>