Audi Allroad BHW TDI conversion.

Later cars don't have an A/C clutch and compressor operation is controlled by a cycling valve or variable displacement unit that regulates the flow of freon. 4.2 C5 Allroad, B6/C6 and MKIV cars all lack a compressor clutch. I put a B6 AWX 1.9 tdi into a B5 and had to swap out the A/C compressor because the control unit for the B5 A/C doesn't produce the proper signal to the A/C compressor.

Learn something every day. Thanks.
On the B5.5 Passat, the Climatronic controls a relay, J44, which controls the clutch. In the non-Climatronic version, the clutch is controlled directly by an AC Cutoff Control Module. The ECU also feeds into this module from pin T94/50.

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What engine control unit did you use?
EDC16 or EDC15p?

Any fuel mileage? lol.

Yes I am curious about the fuel mileage. As you can see in my fuelly, the mileage I get on a 4motion Passat is not as good as on the fwd passats. This is to be expected with the awd and also the W8 Passat is quite a lot heavier than the regular TDI. I don't know how heavy it is now without the W8 engine however but probably still heavier with the larger fuel tank and AWD etc.

Curious what yours will be!

Do you have any L/100 or Mpg to report? What speed does the engine rev at 100kph?

Windex said:

Do you have any L/100 or Mpg to report? What speed does the engine rev at 100kph?

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If the stock Allroad gearing is used revs at 60mph would be about 2300. At 80 mph 3100 rpm.

Comparing to a diesel transmission 60 mph yields 1800 rpm and 80 mph approx 2400.

Okay, so I have still not figured out the A/C yet... The BHW engine that's in my allroad definetly has a clutch on the a/c compressor it's identified as N25 in the wiring diagrams...
So there are many similarities and diffrences between the Allroad and the Passat's A/C systems...
-They both have A/c compressor clutches, that actuate from the same wire gn/ge (green and yellow). When I power the wire directly from the battery, the clutch engages, but even with my heat controls set to LO, no cold air from the vents. (the compressor and lines were serviced yes).
-Both systems have a J44 (a/c cluth relay).
-Both systems seem to have some kind of pressure switch Passat:F129 (a/c pressure switch) Allroad: G65 (high pressure sensor)
-Audi J285 Control Module vs passat J255 Climatronic control module.

So essentially the big thing is is the J255 Climatronic control module vs E87 A/C control head, How do I fool the E87 A/C control head into: 1: Getting J44 relay to energise = A/C clutch to work. 2: Configuring the vents in the cabin to blow the air through the cabin a/c rad.
Fuel economy has been very good thus far. I've averaged 6.0L/100km over about 200km last week. I was driving between 110km/h and 125km/h, this was without the cruise control, so my acceleration wasn't as smooth as it could have been. I will be driving from toronto-ottawa within the next few days with cruise control, we will get a much better idea then.
At 130km/h My rpm is at 2400. 6th gear has a .54 ratio. So at 100 I must be around 2100? Give or take? I'd have to check.
All thoughts on the A/C system are appreciated, I've looked over the diagrams several times now, and I'm running out of ideas.

Ifixit said:

What engine control unit did you use?
EDC16 or EDC15p?

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I'll have to check. I will get back to you.

Wing_man said:

6th gear has a .54 ratio.

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What transmission are you using? .54 is not an 01E gear ratio.

What fault codes are stored in the allroad climatronic module currently?
Is the econ light always on?
No need to fool the clima module it should work as long as the ac pressure switch is functioning correctly you can check this in clima mesuring blocks
I would also check the ac compressor cut out signal from ecu to clima module
(should be a wire in your system not via can)
I will check wire diag for you and see what I can find

3 wires from ecu to clima module

grn/blu clima A2 to ecu pin 37
blk/yel clima A7 to ecu pin 40
blk/grey clima C15 to ecu pin 41

are these connected?
EDC16 or EDC15P ecu?
ECU part number? or just post an autoscan would be helpful

Ifixit said:

3 wires from ecu to clima module

grn/blu clima A2 to ecu pin 37
blk/yel clima A7 to ecu pin 40
blk/grey clima C15 to ecu pin 41

are these connected?
EDC16 or EDC15P ecu?
ECU part number? or just post an autoscan would be helpful

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That is true with the original allroad ECU. But on the Passat BHW ecu, I can't find any correlation to the pins you mention. There are two connectors on the Passat ecu, T60 and T94. To which are you referring?

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Scott_DeWitt said:

What transmission are you using? .54 is not an 01E gear ratio.

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In post 10 he said FTF tranny.

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jonlowe said:

In post 10 he said FTF tranny.

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Yes, an 01E FTF.

http://workshop-manuals.com/audi/a4...hanical_units_transmission_ratios_capacities/

jonlowe said:

That is true with the original allroad ECU. But on the Passat BHW ecu, I can't find any correlation to the pins you mention. There are two connectors on the Passat ecu, T60 and T94. To which are you referring?

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Ok so then he must be using EDC16 ecu (the original NA market BHW controller)

my next question would be is the ecu coding set for climatronic?
I believe the only coding option for that control unit is manual or automatic climate control unless his tuner changed the firmware

BHW with climatronic only has one wire from clima T16B to ECU T94 pin 50 blk/gry
also has a wire from ecu to passat fan module which will also be different on allroad and probably wont effect compressor engagement
Any engine DTCs?
lets check clima DTCs first now can we?

the thing is the clima units are different between the two cars so pinouts/signal may not match up exactly
also, A6 TDI of that era used edc15P in Europe I believe so control scheme in ECU may be different

elsawin is down here right now so I dont have access to allroad tdi wire diagrams but maby someone else does?
mine will be fixed soon...

Why not verify what the real Allroad diesels used regarding pins? Also the 1.9 was put into A6's as well.

Scott_DeWitt said:

Why not verify what the real Allroad diesels used regarding pins? Also the 1.9 was put into A6's as well.

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Thats what I was thinking but no elsa right now..

DTCs would be a great place to start for no compressor engagement IMO

ECU would be EDC15P in the A6 1.9 of that era right scott?

Ifixit said:

ECU would be EDC15P in the A6 1.9 of that era right scott?

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I believe this to be correct for the PD models (2001-2005).

Ifixit said:

Ok so then he must be using EDC16 ecu (the original NA market BHW controller)

my next question would be is the ecu coding set for climatronic?
I believe the only coding option for that control unit is manual or automatic climate control unless his tuner changed the firmware

BHW with climatronic only has one wire from clima T16B to ECU T94 pin 50 blk/gry
also has a wire from ecu to passat fan module which will also be different on allroad and probably wont effect compressor engagement
Any engine DTCs?
lets check clima DTCs first now can we?

the thing is the clima units are different between the two cars so pinouts/signal may not match up exactly
also, A6 TDI of that era used edc15P in Europe I believe so control scheme in ECU may be different

elsawin is down here right now so I dont have access to allroad tdi wire diagrams but maby someone else does?
mine will be fixed soon...

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As I pointed out in post 28, T94/85 also connects to the Passat Climatronic T12/2, 'RPM increase". This doesn't show directly on the ECU side of the ELSA wiring diagram, but does show on the Climatronic side of the wiring diagrams. So there are two connections between the climatronic and the Passat ECU.

Good thought about the coding. That may help him.

Jon

Scott_DeWitt said:

Why not verify what the real Allroad diesels used regarding pins? Also the 1.9 was put into A6's as well.

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Good point. I'll check.

Yes A6 1.9 L with climatronic should be the closest wire diagram match
Although on the ECUs side the pin out won't match as it will be EDC15P
But if there is only two wires from climb a Tronic unit to ECU then it may work with those two wires connected to the right pins

Well, ELSA is giving me fits also. It's not letting me see the engine or climate control wiring diagrams for any A6's with the 1.9 TDI engine.

We really need to understand what the three signal wires between the stock allroad ECU and climate control are. At least on the Passat I was able to find out what the Climatronic signals were. I can't find anything similar for the allroad.

Jon

Ive found one description on the allroad 2.7 diagram:

clima A2 to 2.7 ECU pin 37 grn/blu "Tachometer"
Shows a direct connection beetween clima and ECU with a tap comming off that goes to" Tachometer"
not sure if that is going to be helpful but I believe some clusters have a RPM out square wave signal?
beautiful mitchell wire diagrams

Scott_DeWitt said:

What transmission are you using? .54 is not an 01E gear ratio.

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Yeah my bad Scott, It's a .56 6th.

As for active DTC's I've left my VCDS cable and laptop at my shop in ottawa, I will scan in a few days I'll see what I find. I'll also do some more digging for the pressure switch thing.

The econ light is on when is start the vehicle. If I hit the econ button the light goes off for a few seconds then comes back on.

Wing_man said:

The econ light is on when is start the vehicle. If I hit the econ button the light goes off for a few seconds then comes back on.

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Climatronic is locking out ac due to a system fault then..
check codes and let us know

Ok, got ELSA working. I found that the 2001 A6 with the 1.9 AJM TDI engine uses a climate control in the same family as the allroad, if not exactly the same one; they have variants for w/wo heated seats, NAV, etc. The AJM is the only 1.9 I could find that used a compressor clutch rather than the compressor control that Scott mentioned. In addition, Audi made a running change in the climate control in 2002, and I don't know which one he has or if it even makes a difference in the wiring.
Anyway, pin numbers between the BHW and AJM ecu's don't match at all, but wire colors seem to match reasonably well, discounting for differences in the engine electronics.

The A6 climate control shows:
1. sw/ge (black/yellow) going from A7 to the ECU. This seems to match up with the same function as black/yellow on the Passat ecu, terminal T94/85.

2. ws/bl (white/blue) going from C13 to the ECU. Unfortunately, the AJM ecu has multiple white/blue wires. The connection to C13 on the climate control is interesting because it is only noted for diesels. The AJM ecu has white/blue on terminal 61, but that goes to the EGR valve. It also has white/blue on terminal 15, that indicates it goes to the climate control. I don't know what the function is. Finally, the AJM ecu has a sw/bl changing to white/blue at terminal 20. This appears to be a speedometer related item. The Passat ecu has two white/blue wires, one of which is only used for an additional heater (not for US/CDN), and the other going to the speedo. So I don't know where to connect this wire from C13 on the Passat ecu, or if it is even necessary.

3. sw/gr (Black/grey) going from C15 to the ecu. This appears to match T94/50 on the Passat ecu, same color wire.

4. gn/bl (green/blue) going from A2 to the ecu. This appears to be the engine speed signal. I don't know where this signal is on the Passat ecu, or if it is available there. I would think it would be, but I don't know where. That color wire doesn't appear to exist on the Passat ecu. The Passat climate control has a pin for it, but it doesn't appear to be used on the wiring diagram. I also can't find it on the Passat gauges pinout. They may use the CAN bus on the Passat.

I've got PDFs of the A6 diagrams (and the Passat) if you need them. I'd post them, but there only seems to be a way to post images, not PDFs.

Jon

Wish I had some to add, but when I couldn't figure it out "simply", I gave up and moved onto other far more important items.

jonlowe said:

Ok, got ELSA working. I found that the 2001 A6 with the 1.9 AJM TDI engine uses a climate control in the same family as the allroad, if not exactly the same one; they have variants for w/wo heated seats, NAV, etc. The AJM is the only 1.9 I could find that used a compressor clutch rather than the compressor control that Scott mentioned. In addition, Audi made a running change in the climate control in 2002, and I don't know which one he has or if it even makes a difference in the wiring.
Anyway, pin numbers between the BHW and AJM ecu's don't match at all, but wire colors seem to match reasonably well, discounting for differences in the engine electronics.

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Most of the climate control head differences are cosmetic. The plastic finish changed in 2002 and the seat heater switches are mounted in the head unit. Not sure about the nav, but the head unit is probably slightly smaller. The only wiring differences that I know of are the cars with solar sunroof, there is an additional few wires that go to the sunroof.