f vtec

OK I recently bought a 2001 s8. After a month of owning the car the Ac Vents have stopped working correctly. The driver side will Not allow the AC to flow out the vents. the passenger side blows cold as it should. When the ac is on. The driver side blows the same as out side air temp. the heater seams to work fine on the driver side.
The passenger side Ac is cold but the heater doesnt seam to work as it should.

I'll take any input! Thanx

f vtec

Is there anyone that has any insite on how the system works?

Kneale Brownson

Sounds like air flow flap motor issues. The motor is on the driver side of the A/C housing in the middle of the HVAC well behind the engine. I think you have to remove the plastic rain diverter surrounding the brake fluid reservoir to expose the cover to the flap motor.

Probably your best bet is the on-board diagnostics.

f vtec

Are you talking about the flap that in in the engine conpartment, The one in the center of the rain tray area? I've looked at this part. It does close when the Ac is on.
I've also removed the entire radio section and looked at the control servos. They all appear to move as they should. (I could be over looking one)
What I have noticed is that when the Ac is on, the center of the dash vents. (inside the dash) the driver side blows either warm or out side air temp. Even though the passenger side is blowing cold.
Is there a flap in side that box that controls the Hot and cold for the driver side? If so does anyone know which of the servo motors controls this flap?

Kneale Brownson

From the Bentley repair manual:

*******************

The A/C control head -E87- receives input information from various electrical and electronic components (sensors).
This information is processed by the control head according to specified values and then provides corresponding output signals that control electrical components (actuators).
The A/C control head -E87- is controlled by an internal microprocessor with On Board Diagnostic (OBD) capability. If malfunctions or open circuits occur on applicable components, Diagnostic Trouble Codes (DTC) are stored in memory.
When starting On Board Diagnostic program, always check the stored information with VAG 1551 Scan Tool (ST) or VAG 1552 Scan Tool (ST).
Malfunctions recognized by OBD are assigned DTCs and an indication of the malfunction type. Tables containing all DTCs and corresponding repair information guide technicians through the OBD program.

***************************

Your problem sounds like the kind of thing--sensor misreading circumstances or responding element not responding properly--the OBD testing procedures are designed to diagnose. You need a dealer or the test equipment.

f vtec

Yeah I've tried to used 3 differnet scanner/computers with Vag-com on them. Non have been able to scan the Ac trouble codes.
I have held down the 2 buttoms on the climate head and got the temp screen to display numbers. Like the A6 trouble codes. I just dont know if the Numbers are the same codes for the a6 and a8.?

Kneale Brownson

If you have the correct Ross Tech programming and connector for the car, it should read the HVAC module.

I think the number codes on earlier models were the same (model to model), so I'd guess the A6/A8 codes to be the same, but I don't know that for a fact.

f vtec

OK so I was able to pull these codes
00734
00722
00723

we tried looking at the all data/the vag-com/and cd rom manual.
I cant figure it out. any help?

f vtec

I pulled Both the temp probes that are in the mixing chambers. swapped them around Still the same deal. Ac on the passenger side & no Ac on the driver.

Anyone have any ideas?

Kneale Brownson

From the Bentley:


VAG 1551 scan tool display
Possible cause
Corrective action

00722



Left center vent switch-F183


*Short circuit to Ground /SP

*Open/short circuit to B+ /SP
Short circuit or open circuit in wiring between F183 and A/C control head -E87-
Left center vent switch -F183- faulty
Check wiring for open, short circuit according to wiring diagram, repair as necessary
Test switch F183 => electrical test, => page AUDI-D3-HA01-01-002-0101-146

00723



Right center vent switch-F184


*Short circuit to Ground /SP

*Open/short circuit to B+ /SP
Short circuit or open circuit in wiring between F184 and E87
Right center vent switch -F184- faulty
Check wiring for open, short circuit according to wiring diagram, repair as necessary
Test switch F184 => electrical test, => page AUDI-D3-HA01-01-002-0101-146



00734



Ctr. Vent Pos.Sensor-G142


* Short circuit to Ground /SP

* Open/short circuit to B+ /SP
Short circuit or open circuit in wiring between G142 and E87
Center vent position sensor -G142- faulty
Check wiring for open, short circuit according to wiring diagram, repair as necessary
Check sensor G142, electrical test => page AUDI-D3-HA01-01-002-0101-146

1) This malfunction is only recognized during basic setting
2) Both end stops must be reached
VAG 1551 scan tool display
Possible cause
Corrective action