B4 auto climate control into coupe

[S2central.net]

Good lad...

If you are doing a write up on this, please explain your starting point with photos and such, as it may be different from UK & EU folk wanting to do a 'CCU' - climate control upgrade. My plans have stalled cos of work hassles eating up my life, but thats another story. Good work there.

Guess the job on mine is lining up for the winter now, but hey....

[ShadowofBob]

Yeah I am glad that everything worked out, I was starting to worry I would only get heat or ambient air for a little bit.

There is one thing I wish I could add though. The B4 90 Climate head unit doesn't have support for shutting the heater valve with the vacuum servo I added. The one from a 100 or similar does, but recoding won't let it bypass the speed sensor like the B4 90 one does. Would be nice to be able to close it off when not in use to keep as much residual heat out of the cabin and have the AC as efficient as possible.

[johne]

I've put some tables together of what each pin on the climate computer connectors A - D do and connect to which Paul will post on S2 Central sometime but it would also be good to have a listing of all the different coding options like which one needs a compressor speed sensor, which one needs a water temp. sensor etc.

You could wire your water valve isolate to the recirculate output - that would help at the most critical time but it's not ideal, I know. Otherwise, why not just have a seperate switch to control the valve, you're unlikely to use it more than a few times a year?

For us over here where it doesn't get so hot, I think it's a complication that isn't needed. Also, as the heater circuit is always on, most engines now use that circuit to double as the thermostat bypass circuit during warm up. Without it the only bypass circuit left is via the turbo and the lower plate on the thermostat and I wonder if this is big enough to take the flow. You say the 100 has this option, what does it do to provide a bypass during warm-up?

The first British car I know to have an air blending heater (rather than a water valve contolled one like they all used to be) was the Austin Maxi and it came with a mechanical tap on the heater flow and the instruction manual suggested you turn it off for summer!

Having said that, from the work I've done this is never going to be an "easy" conversion unless someone is willing to make up a bespoke wiring loom. I started with a car that didn't have even manual air-con and the relays for my radiator fan control are controlled to +12v whereas on a manual A/C car they start life as being switched to ground. Those sorts of big differences makes this all a challenge for a plug n play solution.

John

[ShadowofBob]

By bypass I meant that it just shuts of coolant being pumped to the heater core and thus keeps extra heat out of the cabin. The V6 90s didn't have this but instead opted to use the flaps inside the box to seal out heat from the heater core section. I was thinking out using a switch, but I'd prefer to see if there is some control head or coding option that would enable this feature first.

[Jamo]

I've put some tables together of what each pin on the climate computer connectors A - D do and connect to which Paul will post on S2 Central sometime but it would also be good to have a listing of all the different coding options like which one needs a compressor speed sensor, which one needs a water temp. sensor etc.

You could wire your water valve isolate to the recirculate output - that would help at the most critical time but it's not ideal, I know. Otherwise, why not just have a seperate switch to control the valve, you're unlikely to use it more than a few times a year?

For us over here where it doesn't get so hot, I think it's a complication that isn't needed. Also, as the heater circuit is always on, most engines now use that circuit to double as the thermostat bypass circuit during warm up. Without it the only bypass circuit left is via the turbo and the lower plate on the thermostat and I wonder if this is big enough to take the flow. You say the 100 has this option, what does it do to provide a bypass during warm-up?

The first British car I know to have an air blending heater (rather than a water valve contolled one like they all used to be) was the Austin Maxi and it came with a mechanical tap on the heater flow and the instruction manual suggested you turn it off for summer!

Having said that, from the work I've done this is never going to be an "easy" conversion unless someone is willing to make up a bespoke wiring loom. I started with a car that didn't have even manual air-con and the relays for my radiator fan control are controlled to +12v whereas on a manual A/C car they start life as being switched to ground. Those sorts of big differences makes this all a challenge for a plug n play solution.

John

Did this information ever get made public?

[siV6Qcoupe]

Just to say I plan on doing a climate control conversion in the new year when the weather gets warmer (and hopefully drier ) and I too have mulled over weather to base my conversion on the early LHD B3/4 - RHD C4 variant or go with a later B5 variant. The C4 version was appealing but due to the rariety of parts available used and the control valve issue I decided on the A4 varaint but not the early system similar to that used in the C4 but a '99 version.

My car has manual a/c and uses the 2.8 v6 incl. the compressor speed signal. I Have managed to collect all the parts needed apart from the odd connector.

Parts Acquired so far include...

'01 B5 heater box with flap motors - identical moulding to the early '96 A4 but the flap motors are a "mkII" version with sockets rather than pigtails.

'99 B5 control head

'01 temperature sensors which consist of:-
ambient temp sensor (Generic Audi part, 1K thermistor - front of car)
fresh air temp sensor (1K thermistor - located just inside cabin filter aperture)
dash air temp sensor with fan (Saab part but uses an Audi spec. 2K8 thermistor)
central vent air temp sensor (Audi part 15K? thermistor)
footwell air temp sensor (Audi part 2K8 thermistor)
sun sensor (Vauxhall part - unsure of spec but as long as it can tell the difference between night and daylight)

The above sensors have been bench-tested using the control head's diagnostic temperature readings, channels 55 - 62 ('99 spec.)

VAG group generic fan motor control unit (using a C4 style unit rather than '99 A4 unit)

Plugs and connectors from '01 B5.

Unfortunately I have not found a way for the '99 A4 system to control the recirculating function as this is done with a motor/potentiometer flap on the A4 rather than a vacuum activated open/shut flap on earlier cars but then again I never use this function.

Also of note is the current manual a/c ssystem uses an air temperature switch inside the cabin filter box to turn the compressor off in cold near freezing weather, this will no longer be required as the external temp sensors take over this duty.


I still need to acquire the LHD b3/4 dash surround and fixings, does anyone have a specific part number(s) for the parts, I can see many listed but it is not clear which one is for the later climate system?

[mc1]

Hello I live in denver and saw you write up and am intrested in doing the same in my coupe and had a few questions for you ? If you could reply with anumber I could reach you at that would be great . Thanks marc 610 247 4003 I live in englewood

[Ruffiano]

Hello I live in denver and saw you write up and am intrested in doing the same in my coupe and had a few questions for you ? If you could reply with anumber I could reach you at that would be great . Thanks marc I live in englewood

Try sending a private message...

[johne]

Unfortunately I have not found a way for the '99 A4 system to control the recirculating function as this is done with a motor/potentiometer flap on the A4 rather than a vacuum activated open/shut flap on earlier cars but then again I never use this function.

I suspect you'll find that pin D6 on the B5 control head will drive a vacuum operated solenoid for you.

Also of note is the current manual a/c ssystem uses an air temperature switch inside the cabin filter box to turn the compressor off in cold near freezing weather, this will no longer be required as the external temp sensors take over this duty.

The sensor you call the fresh air temp sensor sits in it's place. The control head uses the lower of the temperature from this sensor and the sensor at the front of the car to inhibit the compressor in near freezing conditions.

I still need to acquire the LHD b3/4 dash surround and fixings, does anyone have a specific part number(s) for the parts, I can see many listed but it is not clear which one is for the later climate system?

I posted the part number in one of my posts on the subject.

John

[siV6Qcoupe]

Thanks John!

I know that pin D6 is not used on the '99 head unit and that it is normally used for vac operated recirculation; it will be interesting to see if the functionality still exists. I'll give the head unit a bench test to see if D6 shows any output when the recirculation function is pressed.

I couldn't find the posts regarding specific part numbers but looking through the Audi part catalogue I think these are the numbers for a plain black trim panel and associated parts...

Trim...8A0 820 425 B
Frame...8A0 820 391
Spring Clip... 4A0820 323 (2 off req'd)
Screw x 2

[johne]

Thanks John!

I know that pin D6 is not used on the '99 head unit and that it is normally used for vac operated recirculation; it will be interesting to see if the functionality still exists. I'll give the head unit a bench test to see if D6 shows any output when the recirculation function is pressed.

I couldn't find the posts regarding specific part numbers but looking through the Audi part catalogue I think these are the numbers for a plain black trim panel and associated parts...

Trim...8A0 820 425 B
Frame...8A0 820 391
Spring Clip... 4A0820 323 (2 off req'd)
Screw x 2

The part number on my trim is 8A0 820 425 - there's no "B" on it but I guess that's B for black.

I haven't bothered with the clips, the trim holds in tightly due to the padded dashboard around it.

I can't see my frame number as that's buried under the mass of silicon I used to glue it into the centre dash housing

John

[chapel]

I need to re-read this whole thing, but I have a C4 S6 and it has a bad CC unit. My friend has a B4 90 CC unit for me. So I can use his unit in mine but I have to recode it using a VAG COM?

[siV6Qcoupe]

Anyone further forward on a documented RHD manual2auto A/C conversion?

I've been planning mine on and off for a year or so, I'm at a stage where I've combined the schematics of a '96 A4 with that of my '98 80 Cabriolet A/C system(used a tif file editor).

I managed to get hold of a '96 A4 CC head unit which enables me to use the vacuum actuated recirc function. The central motorised flap unit is actually from a 2001 B5 and is the same as far as I can tell to an earlier '96 B5 unit. An important detail is that most schematics will show the pin layout for the flap motors for LHD cars, on RHD cars the motor and potentiometer pins are reveresed. In my case I wasn't able to get hold of a complete A/C loom so I have a few custom looms and splicing to do. The CC head unit is basically replaces the A/C compressor clutch relay module and manual control unit. The heater fan relay disappears but can be reused to switch the compressor clutch on and off as controlled by the CC head unit now. The 3-speed engine cooling can be retained as it's virtually a separate entity with only the coolant fan control relay being connected to the CC unit. A 3-pin blower fan control unit from a A3 or A4 will be needed to control the blower motor speed, this will need to be grafted onto the left side of the air duct near the blower to cool the heatsink. A complete A4 heater system would solve this as all the components would be included but I don't really want to disconnect my working A/C system and pay the expense to drain and refill it.

At the moment I have a basic system set up indoors powered to a 12v battery with temp sensors and flaps wired into the CC head unit. It's quite strange to see the heater flaps twitching and changing like it has some sort of artificial intellegence of it's own!
One thing that I noticed is that the older '96 A4 headunits do seem to suffer from degradation in the display and of course they use the old bulb backlit system. The later A3/4 units have an LED backlit display that looks as though it can be swapped over to the older bulb lit head units.

[S2central.net]

I like this thread... I rediscovered my CC head unit in the dead project cave... From an LHD RS2 which I can recode for RHD

I have a notion that other CC head units might not be programmable for S2 application unless they have an option to ignore the compressor speed signal... Or you swap out the compressor to one that provides the signal but even then it might be off as the rpm wil not be in alignment with 5 pot. Except a CC unit that is compatible with AAN motor i.e C4 platform

[johne]

Anyone further forward on a documented RHD manual2auto A/C conversion?

............An important detail is that most schematics will show the pin layout for the flap motors for LHD cars, on RHD cars the motor and potentiometer pins are reveresed.

...........A complete A4 heater system would solve this as all the components would be included but I don't really want to disconnect my working A/C system and pay the expense to drain and refill it.

My guide on how I converted my car is almost ready to go public with.

It's not true to say that on RHD drive cars the connections to the motors are reversed, they are not. Audi made a mistake in the wiring to the temperature flap motor which they got round by changing the wires over at the intermediary plug/socket between the control unit and the motor. The remaining flap motors are unchanged from the wiring diagrams. They'll be more details in my guide.

A complete A4 system won't solve your problems as it won't fit! The complete A4 system is too wide to fit our cars and the air-con pipes come out in the wrong place. You have to end up with a hybrid system which as you say has the benefit that you don't have to change your S2 air-con components.

John