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TDI Conversions Discussions on converting non TDIs into TDIS. More general items can be answered better in other sections. This is ideal for issues that don't have an overlap and are very special to swaping engines.

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Old July 10th, 2017, 15:03   #1
GoremanX
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Default How Did Others Get A/C To Work on BHW Swap?

I've been driving my TDI-swapped Audi A4 for a few weeks now. It's awesome, but the lack of A/C has been annoying. So I finally got my A/C system charged today... and nothing. The compressor doesn't seem to be cycling on/off. My guess is the Climatronic module isn't doing its job for whatever reason.

When looking at the BHW ECU Coding section in VCDS, there's a panel that pops up stating:

Quote:
Engine Control Unit (J248) Coding
0050074 - Automatic Climate Control
0150034 - Manual Climate Control
Mine is coded to 0150031 because I changed it to accommodate a manual transmission. It was originally 0150034. But any attempt to change it to 0050071 is failing with the error message Error 31: Request out of range.

As far as I know, automatic climate control was only available on the GLX trim of the B5.5 Passat, and the TDI wasn't available on that trim. But I know for a fact that others have swapped BHWs into miscellaneous cars (A4s, allroads, etc) and got Climatronic A/C working. So what am I doing wrong?

There are no error codes in the Auto Climate Control module.
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Old July 10th, 2017, 16:31   #2
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Further info that I forgot to include above:

I did code the Auto HVAC module for a diesel with left hand drive (00143).

When running the output tests, the A/C compressor clutch does get engaged, so the climate control unit does have control over it. But it only stays on for about a second before disengaging again.

If I try to engage the compressor clutch with direct 12v while the engine is running, it does engage, but no cold air blows. Low side sits at 30psi, and high side is at 90psi (the high side seems low to me). It's very hot and humid out right now.

The electric radiator fan comes on when I turn on A/C.
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Old July 10th, 2017, 18:06   #3
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Pressure swiitches? Sounds like what I would expect if it started, and pulled too low on the suction side, and hit the low pressure cut out. This is supported by the low pressures and lack of cooling as well - on a hot day, no way is 90 PSI going to condense to liquid. How did you determine charge status?

Doing a bit of research, for an R134A system, and 90 degrees ambient, you should have more like 50 on the low and 260 on the high . . . and both sides low, again, points to low charge.
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Old July 10th, 2017, 19:10   #4
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Yeah, both those pressure numbers seemed low to me, but I was under the impression that the pressure switch monitors the low side, and 30 psi should be high enough to allow the compressor clutch to turn on. I had it charged at a local shop because I wanted a nitrogen purge first (which I'm not equipped to do).

My concern is that with the ECU not coded for Climatronic, the HVAC controller may not be getting a signal from the ECU that permits it to run the compressor.

If it was a lack of pressure preventing the clutch from engaging, I'd expect to see an error in the Auto HVAC module.
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Old July 10th, 2017, 19:56   #5
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If it's hot, 80f or so, you should be seeing 50psi low side and 180-210psi high side. And the AC should work fine no matter what if you jumper the clutch on. There are no controls other than the compressor clutch and the blend doors, the evaporator should still get cold (feel the pipes). It just sounds undercharged to me. I would charge it again, put some dye in it and look for leaks. I've been struggling this year with AC leaks on all my vintage VW's, dye is your friend...

I got my audi climatronic working on my BHW swap by using an audi AWX EDC15P ECU that was compatible with all the B6 modules. It worked for s good 5 minutes the first time before the charge all leaked out, fooled me since it held a vacuum fine... But at least it had dye in it so the problem was very obvious, compressor leaked from every gasket. New compressor and all is well.
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Old July 10th, 2017, 19:56   #6
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You said it engages and then cuts off, no? That's what I based my commentary on. And not sure how much good the N2 purge will do, since you still need to pull and hold a vacuum to clear moisture and non condensibles prior to charge. N2 with a small amount of refrigerant is a good leak test gas, though . . .

And even if it's a coding error, you *DO* have a charge problem as well - the manual run with 12V on the comp pretty much proved that . . .
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Old July 10th, 2017, 20:35   #7
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Quote:
Originally Posted by tadawson View Post
You said it engages and then cuts off, no?
I meant only during the output test. I'm not sure if that's how the test is supposed to behave. Other than that, the HVAC controller refuses to engage the compressor at all, no matter how much I ask it to. I can only engage the compressor clutch by forcing 12v into it manually. You're right, the charge clearly seems low based on those numbers. But I don't think it's low enough to trip the pressure switch. I think the minimum pressure to trip the switch is 22 psi.

Quote:
Originally Posted by QuickTD View Post
I got my audi climatronic working on my BHW swap by using an audi AWX EDC15P ECU that was compatible with all the B6 modules. It worked for s good 5 minutes the first time before the charge all leaked out, fooled me since it held a vacuum fine... But at least it had dye in it so the problem was very obvious, compressor leaked from every gasket. New compressor and all is well.
Supposedly the shop that filled the system did include dye. I just went out with a really bright UV light, and I don't see a spot of dye anywhere. Mind you I'm not seeing any dye in the opening of the schrader valves either, so maybe they forgot to include the dye... it's pitch black outside and I turned off all ambient light sources, so I can see very clearly with the UV light.

The compressor is new, the condenser is new, the dryer is new. All of the lines are either new or good used. I replaced all O-rings. Everything that wasn't new (including the evaporator) was flushed prior to installation, and the system held a 29 in-hg vacuum for a month without any leaks. I made sure to add the required amount of PAG-46 oil before assembling it all. I used aluminum anti-seize on all joints. I can't think of any step I missed, with the exception of changing the orifice tube (the old one looked brand new but was really hard to get out, so I just left it there).

With everything cooled down and at rest, the system is showing 85 psi on both sides, which seems normal to me based on ambient temperature. Not an indicator of how filled it is, but it seems to imply there are no leaks in the system.

I'll call the shop tomorrow and ask for more details about what was done and how they determined that it was filled "enough".
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Old July 10th, 2017, 20:56   #8
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The 85 psi at rest just means there is a sufficient amount of refrigerant to have some liquid present in the system. Static pressure can't really indicate how much. I find the Passat style AC systems very sensitive to undercharge. 100 grams low and they'll hardly cool at all. I lean towards overcharging them a bit, +50 grams (~1-1/2oz), never had any trouble and they definately cool better.
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Old July 10th, 2017, 22:26   #9
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Yeah, typically these systems need to be charged by weight . . . jou just need to determine what your system is closest to, and put that in for starters . . . should be pretty close . . .

Sorry I can't help more on the coding, and also sorry I missed the output test relevance of the operation. If nothing else, you know the module can drive the compressor clutch, though . . .
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Old July 11th, 2017, 05:22   #10
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B5 A4 and Passat A/C systems are essentially identical. In fact during the swap, I left the original 1.8T A/C system in place and just bolted it up to the BHW without any modifications. The only reason I ended up replacing so many components is because the original condenser took a bit of a beating from all those times I tried and failed to step over it I figured if I have to replace the condenser, I should go all out and refresh the whole system. There were a LOT of totally-seized joints when I started taking it apart, hence all the new hoses. Factory spec calls for 700g, so I'll ask the shop how much they put in there.
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Old July 11th, 2017, 09:35   #11
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They definitely under-charged it. Less than 20oz were put into the system. This will be rectified tomorrow. They also didn't put any dye, because the only dye they had was mixed with oil and it wasn't the right kind of oil for my system. This will also be rectified tomorrow.

Still doesn't explain why the compressor isn't being turned on by the HVAC controller, though...
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Old July 12th, 2017, 11:54   #12
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This is great that you've posted up on this problem.
I have an 04 GLX 4mo w/BHW.
I am dealing with the exact same problem (aside from the fact that I topped mine up).
Charge is now 50psi at 28*C ambient. Blows cold when I jumper to the compressor.
No codes in HVAC module.
It's very hot and smokey (due to all the forest fires in my area), so driving with the windows down is less than ideal.
So....for now I use the jumper!
I may even put it on a switch on kick panel. Ideally to power the relays and do the job that the Climatronic isn't.
I suppose the risk is forgetting to turn the switch off...

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Old July 12th, 2017, 12:53   #13
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Quote:
Originally Posted by B4Ugo View Post
This is great that you've posted up on this problem.
I have an 04 GLX 4mo w/BHW.
Nice! I almost considered doing the exact same thing instead of my A4, except I love my car too much

Quote:
Originally Posted by B4Ugo View Post
So....for now I use the jumper!
I may even put it on a switch on kick panel. Ideally to power the relays and do the job that the Climatronic isn't.
I suppose the risk is forgetting to turn the switch off...
LOL! I bought a "Funk" switch for my dash a couple years ago that I never found a use for, maybe that would be a good one.

System is charged adequately now, and there's dye in the refrigerant. No perceivable leaks. System blows ICE COLD when I feed 12v to the compressor. But the HVAC controller still refuses to engage the compressor clutch. I'm convinced this is due to the ECU coding.

Here's the conundrum: Climatronic was only available on the Passat GLX trim, but the TDI wasn't available on the GLX trim. So as far as I know, there are no B5 Passat TDI ECUs with the required functionality to drive the Climatronic unit. That means there's nowhere to get the functionality from and add it to the image that gets flashed to the ECU.

One option would be to do as B4Ugo proposes: add a switch to turn on the compressor manually. I don't really like it, it's a kludge, but it would work. Another option would be to figure out what signal the HVAC controller expects to see from the ECU, and fake it. Maybe it's as simple as piping 12v or 5v into the necessary wire. I don't really like that either, because it means I lose whatever compressor cutoff signal the ECU is supposed to send under certain conditions.

Ideally, I'd like to be able to just find the required ECU functionality somewhere and figure out how to get it added to my tune. I swear I remember someone mentioning that they got Climatronic to work with an EDC16 ECU on their BHW-swapped allroad... but I can't remember who. It involved adding a wire to the ECU or something.
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Old July 12th, 2017, 16:14   #14
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I agree.
I dislike the kludge also.
But we're never going to get to the bottom of this with cooked brains.
Fwiw, forum member stp359 claims the bhw swap w/clima is plug and play (04 GLX), but he did his own homebrew tuning.
I suspect it's a possibility that it has something to do with our Malone tuning. Certainly not pointing any fingers...
Love those guys.
But there is commonality in our issues. I get the exact same message when I try and enter the coding.
So I will Kludge on until we find a solution
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Old July 12th, 2017, 16:22   #15
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In the meantime, I will continue to lament my SMF setup, and drive at higher RPMs than necessary to prevent the dreaded harmonics...
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