Climate control flap actuator motors
From Knowledgebase
Contents |
Application
- Model: 100, A6, including UrS4, UrS6 and V8 models
- Year: 1988-1997
- Platform: C3, C4
- Type: 44, 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 have a look at the Climate control codes. You may 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 in the case of the Central Air Flap Motor (V70) and the Footwell/Defroster Flap Motor (V85).
Flap Motor Tray Removal 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 and centre console. I also usually remove the driver's storage compartments, the glove box, 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. 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.
When removing the motors from the tray, 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.
Actuators
Service the actuators according to the excellent pdf from Marc.
Central air flap motor V70 with position sensor G112
4A0 820 511 (blue connector housing)
This is my best guess at the wiring:
- 1 White Motor+
- 2 Brown Motor-
- 3 Grey Pot +
- 4 Green Pot ground
- 5 Yellow Pot wiper
Potentiometer is 4.85 kΩ
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 500 Ω (short arm of L against end stop) to 4.7 kΩ (long arm of L against end stop)
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.
Temperature regulator flap motor V68 with position sensor G92
443 820 511 A (black connector housing)
Identical to others - I forgot to measure the value of the potentiometer!
As this actuator is in the engine bay (or close to), I would expect it to give more problems than the other actuators - particularly with the the potentiometer. So far, this hasn't happened to me - one car had all three actuators fail, the other car had two actuators fail. In each case, it was due to motor problems rather than potentiometer problems.
In RHD cars, this actuator can be removed without removing the windscreeen wiper motor or mechanism. I believe the wiper motor and mechanism need to be removed in the case of LHD cars. In both cases, access is extremely restricted and you need either a stubby Phillips or a mini ratchet to get at the screws on the cover that protects the actuator fro the elements. If someone has been in here before, expect to find several broken screw holes on the cover.
Motor
The motor used in the actuators is made by Bosch and has the following markings:
- 1 397 220 243
- 7V
- 5265 (or some other four-digit number)
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 will vary depending on the phase of motor. It appears to be a three-winding motor - probably wound in star configuration. Between any two sections of the commutator there is a resistance of 28Ω - that would imply a star with 14Ω windings. Expect to measure about 28Ω (or 21Ω if one of the brushes is bridging two segments of the commutator).
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 use a 3.5mm drill bit with some 400 Wet/Dry sandpaper wrapped around it to reprofile the brushes.
I've fixed four completely dead and four failing actuators so far using this method. Three 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.
With no load on the motor, current drawn from a 7V supply is between 20 and 30 mA. After refurbishing the motor, it might be a good idea to run it for several minutes in each direction to allow the brushes to bed in - the current will probably drop slightly during this run-in period.
Climate Control Head
One of my actuators 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.
The L4940V85 regulators are commonly available (Farnell, etc.) for less than £2. The TCA2465 op amps are more difficult to source - I thought they were obsolete, but some have appeared on eBay recently for just under £20.
Look for signs of overheating on the PCB underneath the regulators, or on the metal tab of the regulators and replace if necessary. 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 actuators 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.
External links
- Reparaturen am AUDI A6 C4: alle 4 Klimastellmotore reparieren
- Marc's pdf on AC Control Servo Repair
- Climate Control Head Unit Fix on AudiWorld
Paul Heneghan 23:45, 13 September 2009 (BST)
