Application

Model: 100, S4, A6, S6
Year: 1992-1997
Platform: C4
Type: 4A

Disclaimer

This page contains things I've worked out from a mixture of:

• Haynes manual
• Bentley manual
• Research on the web
• Reverse engineering circuits
• Making measurements on electrical circuits

There are no guarantees as to the accuracy of any of the information here.  Before trying any of the suggested procedures, please verify for yourself that the information is applicable.

Also, my experience is with right-hand-drive UK spec cars; US and European cars differ significantly.

Symptoms

One or more of the following:

• Can't change temperature
• Can't get air to switch between dash vents and defrost/footwell vents
• Can't get air to switch between defrost vents and footwell vents

Using the diagnostic channel on the climate control display (if you don't know how to do this, see http://www.audifans.com/kb/Climate_control_codes), you get one or more of the following codes:

• 08.5 Temperature Regulator Flap, static block
• 08.7 Temperature Regulator Flap, sporadic block
• possibly other 08.x codes
• 11.5 Central Flap, static block
• 11.7 Central Flap, sporadic block
• possibly other 11.x codes
• 13.5 Footwell/Defroster Flap, static block
• 13.7 Footwell/Defroster Flap, sporadic block
• possibly other 13.x codes

If you get multiple codes, then it is probably a good idea to start with the Central Flap actuator (servo), as a faulty one of these has been known to cause multiple fault codes to appear which go away when the actuator is fixed/replaced.

The equivalent DTC codes from a 1551, VAG-COM, or similar, would be:

• 00603 - Positioning Motor for Footwell/Defroster Flap Motor (V85)
• 01271 - Positioning Motor for Temperature Flap Motor (V68)
• 01272 - Positioning Motor for Central Flap Motor (V70)

Diagnosis

It is tempting to blame the Climate Control head, but this is rarely at fault.  The problems are nearly always due to failed motors in the actuators.  Out of 10 cases that I know of, only one of them had a faulty CC head, and in fact the reason it was faulty was due to a short circuit in the motor in the actuator that had caused a regulator in the CC head to blow.

If you have access to another CC head, try substituting it and see what happens.  If one of the motors has gone short circuit, this could cause the regulator in the CC head to blow, but I think this is only likely if the short is there for an extended period.  Do this at your own risk!

Once you have satisfied yourself that the actuators are at fault, then you have to get to them - not easy!

Procedure

The Central Air Flap Motor (V70) and the Footwell/Defroster Flap Motor (V85) are both located on a black plastic mounting tray that is located behind the radio and climate control head.  You need to remove the rear console, centre console, driver's storage compartments and the glove box.  The Haynes manual has a pretty good description of this.

It is also useful to remove the ducting that supplies the face vents for the rear passengers and the two right-angle large-diameter junction pieces that are partially in the way - you should then have a clear view of the tray.

Move the front seats fully back and then remove the tray that holds the two flap motors.  There is one (gold/silver) screw holding each actuator to the flap, and one (black) screw at each end holding the tray in place.  The tray should then unhook, and come forward and out.

Be careful with the white plastic connecting link (4A0 820 341) that goes from the actuator to the black relay lever.  They're fragile!  You should be able to prise off the clamping washer, but go carefully.  The black relay levers just lift out if you rotate them to the correct angle.  You can pop the balls out of the sockets on the red and blue connecting links - it's no harm to lubricate these joints.  Service the actuators according to this excellent pdf from a chap called Marc

Here are some additional notes I made:

Central air flap motor V70 with position sensor G112
4A0 820 511
Blue connector housing

This is my best guess at the wiring:

Potentiometer is 4.85k

When +ve is applied to 1, the output shaft turns clockwise (as viewed looking at the L-shaped actuator on the output shaft.

The wiper on the potentiometer varies from 500R (short arm of L against end stop) to 4.7k (long arm of L against end stop)

Motor markings:
1 397 220
243 7V
5265

The motor is a 7V motor.  See below for a description of how the Climate Control Head generates the 7V.  If you haven't got a source of 7V for testing, you'll probably get away with using 12V for short periods of time (no one has reported blowing one up yet).  Don't apply 12V and leave the motor stalled for any significant length of time though!

Due to the commutator, the resistance of motor varies depending on phase of motor - usually in the range 20R - 40R. 30R is typical.

If the resistance doesn't seem right, and the motor won't run off a 7V supply, then it's worth stripping, cleaning, lubricating and rebuilding the motor and actuator according to the pdf listed above.  I've fixed three completely dead and three failing actuators so far using this method.  Two of the dead ones had gone short circuit due to brush dust filling the gaps in the commutators.  The other one had gone high impedance due to poor contact at the brushes. 

Current drawn from a 7V supply is just over 20mA for a working one, and about 30mA for my reconditioned ones (brushes not worn in yet?)

Footwell/defroster flap motor V85 with position sensor G114
4A0 820 511 B
Red connector housing 

Identical to V70, except value of potentiometer is 4.39k.

Positioning Motor for Temperature Flap V68 with position sensor G???
443 820 511 A
Black connector housing

Identical to others - I forgot to measure the value of the potentiometer!

I measured the motor windings in this one. It appears to be a three-winding motor - probably wound in star configuration. Between any two sections of the commutator there was a resistance of 30R - that would imply a star with 15R windings.

As this servo is in the engine bay (or close to), I would expect it to give more problems than the other servos - particularly with the the potentiometer.  So far, this hasn't happened to me - one car had all three servos fail, the other car had two servos fail.  In each case, it was due to motor problems rather than potentiometer problems.

Climate Control Head

One of my servos still didn't appear to work after I'd reconditioned it, and I traced (by substituting for a good one) the fault to the Climate Control Head.   I did a spreadsheet of the pinouts and also I opened up the unit, reverse engineered the faulty drive stage and drew a crude circuit diagram.

There are two 8.5V regulators (ST L4940V85), one set to deliver 8.5V, the other set to deliver 9.2V.  Each of these regulators supplies two dual power op amps (Siemens TCA2465).  Although there are four dual op amps on the circuit board, in UK spec cars there is no airflow flap motor, so only three of the four channels are used.  The op amps use their dual outputs to provide a differential drive to both terminals of the motor so they can generate voltage in either polarity to drive the motor in either direction.

Look for signs of overheating on the PCB underneath the regulators, or on the metal tab of the regulators and replace if necessary.  It's not expensive (£1.33 from Farnell).  That fixed the fault for me - cheap fix!

By the way, perceived wisdom on various mailing lists and web sites indicates that the Climate Control Heads are rarely the problem.  The most likely culprits seem to be the servos themselves, and it's nearly always brush/commutator problems.

I've noticed quite a few CC heads appearing on eBay recently.  Many of them come from Lithuania and are not outrageously expensive.  I'd appreciate some feedback from someone who has used one.

Here's an article that I found useful:

Re: defroster '93 100cs
User account number (aid): 62432 
Posted by bigeyes on 2003-12-27 08:02:29
In Reply to: defroster '93 100cs posted by Jeffrey K. on 2003-12-26 13:08:07

There are three of these servo motors on my '92 100CS. 

1-Part # 4A0 820 511 Central Flap Motor (blue connecter) it is located under the dash behind the radio and CC. (PITA to get out) 

2-Part # 4A0 820 511A Temp. Regulator Flap Motor (black connecter)located under the hood in the A/C plenum chamber on the left (drivers) side of the blower housing. (I had to remove windshield wiper motor assembly to get it out) You can see it at http://www.audiquattroparts.com/heater_servo_motor.htm 

3-Part # 4A0 820 511B Footwell/Defroster Flap Motor (red connecter)it is located with item 1. 

Go to taylorautomotive.com and do a part # search for items 1 & 3. These are Audi numbers but they will work in the search. 

None of the flaps would work on mine but only the central flap motor was bad. After replacing it all motors worked properly. 

Hope this helps some.

http://www.taylorautomotive.com


Thread:
defroster '93 100cs - Jeffrey K. 2003-12-26 13:08:07 (63 views) 
Re: defroster '93 100cs - bigeyes 2003-12-27 08:02:29 (47 views) 
I think this is controlled by the flap in the windshield cowling... - marcogyver 2003-12-26 18:53:27 (35 views) 

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