B4 auto climate control into coupe

[ShadowofBob]

Sorry for anyone trying to access this recently, my old free webspace provided by my ISP was ended. I still have all the files and will get them back online in the next few days on my own hosting service.

[shurhend]

Sorry for anyone trying to access this recently, my old free webspace provided by my ISP was ended. I still have all the files and will get them back online in the next few days on my own hosting service.

Hi!
any chance to see this thread with pics again?

[ShadowofBob]

Pics and document updated. Sorry about the delay.

[Nuvo]

Pics and document updated. Sorry about the delay.

Do you have a new link to your updated doc?
edit: link is working now.

[Mcstiff]

I may give this a go!

[smittoid]

B4 versus B5 climate control head unit

Hi everyone,

I am doing a B4 Climate Control upgrade to my US 1990 Coupe. This thread and ShadowOfBob & JohnE's documents have been a huge asset!

I have acquired most of the parts I believe I need:
B4 Climate Control housing, complete with wiring harness, servos, evap, blower
B5 Climate Control head unit
(Head unit is from a 1997 A4 - I believe it is an 8D0 820043H but the part # sticker is missing)

I am working on getting the whole setup operating on the bench.

• I have the 3 temp sensors hooked up and closed the circuit for the low-pressure switch.
  
• I have the K line plugged in to VAG-COM.
  
• Diagnostics are working - so I can pull fault codes and read the measuring blocks.
  
• Recoded the head unit to 00142 so the CC head will not look for the compressor speed signal.

I am seeing the following fault codes come up:

• Temp regulator flap motor potentiometer - static / sporatic open
• Central flap motor potentiometer - static / sporatic open

The foot/defrost flap works perfectly.

The "air flow flap" never seems to operate, but does not throw any faults.

With these potentiometer faults, the system seems to disable the flap servo in question, and I am then unable to operate the servo with the head unit controls.

Occasionally I have been able to clear the fault with VAG-COM and the head unit will re-enable the servo, but it is definitely intermittent and the faults come back pretty consistently.

I've tried cleaning the potentiometers with Freon, and measured resistance through the range. Measured 0.5K ohm through 4.9K ohm on both of the servos from the connector.

All 3 motors operate OK with 7-9V applied, forward, reverse. One sparks a little bit, so I am looking at cleaning it out.

I've tried swapping the servos to see if it is a wiring / harness issue on one plug. This worked in one case.

Questions:
Is the B5 CC head unit compatible with the older harness and servos?
Wondering if there is a resistance difference or something. When I unplug a servo and pull the fault codes, the head unit accurately reports the missing servo.

Am I missing anything here?
My next step is checking the wiring harness and servo connectors on the harness itself for intermittent connections.

Thanks,

Smitty

[johne]

I am seeing the following fault codes come up:

• Temp regulator flap motor potentiometer - static / sporatic open
• Central flap motor potentiometer - static / sporatic open

The foot/defrost flap works perfectly.

The "air flow flap" never seems to operate, but does not throw any faults.

With these potentiometer faults, the system seems to disable the flap servo in question, and I am then unable to operate the servo with the head unit controls.

Questions:
Is the B5 CC head unit compatible with the older harness and servos?
Wondering if there is a resistance difference or something. When I unplug a servo and pull the fault codes, the head unit accurately reports the missing servo.

Am I missing anything here?
My next step is checking the wiring harness and servo connectors on the harness itself for intermittent connections.

Thanks,

Smitty

There is no "air flow flap" on the B4 unit - well there is but it isn't worked by an electric motor it's worked by a vacuum servo and we know it as the recirculation flap. As you've noted, the CCU doesn't seem to care.

I don't think there's a problem between the servos and the B5 CCU as the servos are unchanged through much youger cars. The potentiometer resistance value doesn't matter much, the CCU is measuring voltage from the potentiometer centre wiper not resistance.

What I found was that for my temperature flap the motor was going in the wrong direction to the expected output from the position potentiometer and I had to swap the brown and white motor wires over. Check in manual mode if you command max temperature does the temperature flap go to the hot position in the heater unit? If not try swapping the wires over.

John

[MJF]

Old but interesting thread. I'd like to fit hvac to my 89 B3. Even B4 with air condition seems to be extremly hard to find nowadays. I see here are posts of installing B5 box in RHD cars, will B5 box fit to LHD cars too? B5 parts are still easy to find.

[M2ki]

B4 digital climate parts for interior can be found here for a ~ 100€.
I would be extra and buy a plug and play parts from B4, rather than spend days making custom wiring and parts.
You still need the B4 center console and trim for the climate controls.

[MJF]

Yeah, B4 parts would be easier, if only I could find those.

[M2ki]

Asked about one local parts car today, idiots only took the engine a scrapped the rest. Dual airbag dash, pyro seatbelt tensioners, digital climate etc.

[Jaantrag]

Not sure if this is the right place, but with all the technical info on this topic, anyone knows what would cause the hot/cold air flap to operate opposite to what it should ? .. I have a original Auto AC and when the display says HI it blows cold, and LOW blows hot. not that bog of a deal, but since i have to redo the flaps insulations might dig into that problem aswell.

[newsh]

Not sure if this is the right place, but with all the technical info on this topic, anyone knows what would cause the hot/cold air flap to operate opposite to what it should ? .. I have a original Auto AC and when the display says HI it blows cold, and LOW blows hot. not that bog of a deal, but since i have to redo the flaps insulations might dig into that problem aswell.

Is it a vacuum servo on the flap? If so the vac line may be on the wrong port, if it's electrical the motor is possibly reverse wired?

[johne]

See my comment in post #112 above.