[1.6 FSI Climate control + ECU Compressor Intervention]

E

Evripidis

Member
Hi all,

Here goes another one for the aficionados;

The AC blows excellent cold air in the 37 degree Celcius heat of Cyprus but it is intermittent and having borrowed @67boris VCDS I have found out that in Measuring Blocks under HVAC, block number 002 I get a number 12 in the cells that according to ELSA means:

12* Compressor off Air conditioner compressor intervention is currently active (see display zone “1”) Air conditioner compressor intervention was active for more than 12 seconds (display zone 2...4)

Air-conditioner compressor shut off by the engine control unit; interrogate the fault memory of the engine control unit → Relevant Workshop Manual, Ignition and Injection System; Repair group 01

But there are no faults stored in the engine ECU (there is a NoX related DTC that I have erased). This means the comrpessor is being shut off by the ECU for some reason that is not being reported. Any ideas?

Regards,
Evros
 
I believe the compressor is shut down if the refrigerant gas pressure goes below a certain level. May just need regassing maybe?
 
Hi, not the case I am afraid. The G65 reads correct pressure and so do my gauges. And when it is ON the pressures are whithin range for the ambient temperature right now.

Fault code 12 on block 002 is related to the Engine ECU requesting the Climate unit to turn off the compressor via CAN bus messaging. There is info on the Ross-tech website as well. What I cannot find out is what causes the ECU and why this fault is not reported. Unless this is not a fault and happens under decelleration to aid with the vacuum (source: ross-tech).

Evros
 
Runs when the AC is running yes. The problem is intermittent. When it runs it runs fine. It will run and in the middle of a journey it will stop and then will be back again next time I turn the ignition off/on and so on. This alligns fine with the error code 12 mentioned above.
 
OK, I have verified that this error is reproducible when braking.

So when you are on the highway and press the brake pedal slightly the AC will turn off with error code 12 in block 002 of the HVAC. This agrees with the info found on the ross-tech website; the ECU decides it needs all the vacuum it can get and turns the comrpessor off. The compressor will never turn on again until next time the ignition is cycled.

Any info is welcome because I was not able to find anyone else experiencing it other from some people on the ross-tech forum.

Evros
 
Vacuum leak? There must be a sensor to monitor this if the ECU is deciding to disable the compressor, make a log of the vacuum when braking and check against the expected range or another car.
 
I assumed it would have reported the leak but in any case revs are rock solid on idle no hunting, and all vaccum hoses have been replaced when I did the intake flaps.

Checking against another car would be ideal. I have returned the VCDS to @67boris though so this has to happen at a different time.
 
Catnip64 said:
Vacuum leak? There must be a sensor to monitor this if the ECU is deciding to disable the compressor, make a log of the vacuum when braking and check against the expected range or another car.
Click to expand...

Come to think of it. It could be one of the brake servo hoses ?
 
Hi all,

I keep coming back to this issue because it is very annoying. I have found some info on a Skoda forum

https://www.briskoda.net/forums/topic/205880-air-con-problem/?do=findComment&comment=2480253

The person there mentions that if a comrpessor is replaced then it needs to be "ran-in" using VCDS. I assume it is a calibration procedure since the ECU is allowed to turn it off (it needs to know the compressors curve so to speak).

Has anyone done this before using VCDS on the A2? I think it maybe listed as a climate panel adaptation/calibration or something. On the Ross-tech website I could find this

http://wiki.ross-tech.com/wiki/index.php/B109E#B109E.2F9477872_-_AC_Compressor_First_Run-In

Regards,
Evros
 
I would like to resurrect this thread. @Evripidis, did you ever find out what's wrong? My 2015 Audi A5 is doing the exact same thing, shut off condition 12, mostly during braking at a stop light. But it ONLY does it when the engine is not warmed up, and it's hot as hell inside or outside. The compressor switches off for like 20 seconds, then comes back on. Very small issue, but I'm curious to what it is and hopefully it won't get worse.
 
event3horizon said:
I would like to resurrect this thread. @Evripidis, did you ever find out what's wrong? My 2015 Audi A5 is doing the exact same thing, shut off condition 12, mostly during braking at a stop light. But it ONLY does it when the engine is not warmed up, and it's hot as hell inside or outside. The compressor switches off for like 20 seconds, then comes back on. Very small issue, but I'm curious to what it is and hopefully it won't get worse.
Click to expand...
First, the compressor does not switch off, ever, it's driven by the aux belt, and is rotating whenever the engine is. There is electrical control of the flow rate of refrigerant.
The ECU will reduce flow to minimum, (to reduce the load on the engine), if the load on the engine, presented by the compressor is too high, ie cold engine, and high AC demand, (high ambient).
I suspect that's what is happening here.
Mac.
 
PlasticMac said:
First, the compressor does not switch off, ever, it's driven by the aux belt, and is rotating whenever the engine is. There is electrical control of the flow rate of refrigerant.
The ECU will reduce flow to minimum, (to reduce the load on the engine), if the load on the engine, presented by the compressor is too high, ie cold engine, and high AC demand, (high ambient).
I suspect that's what is happening here.
Mac.
Click to expand...
Check Group 57 using VCDS.
See the VCDS Group and Block Guide I posted a while back, to complement @Andrew new FSI label file. Use that file when you scan an FSI engine please.
Mac
 
PlasticMac said:
First, the compressor does not switch off, ever, it's driven by the aux belt, and is rotating whenever the engine is. There is electrical control of the flow rate of refrigerant.
The ECU will reduce flow to minimum, (to reduce the load on the engine), if the load on the engine, presented by the compressor is too high, ie cold engine, and high AC demand, (high ambient).
I suspect that's what is happening here.
Mac.
Click to expand...
Ok. I'm aware of that, it's clutchless. I just use old terminology. Either compressor on or compressor off. So what you're describing, you're saying it's basically normal that it's happening and it isn't an issue. Also, I don't have VCDS. I use third party scantools that pretty much shows me what VCDS shows. What does group 57 show? Also my engine isn't the older FSI, it's TFSI ea 888 gen 2.
 
event3horizon said:
Ok. I'm aware of that, it's clutchless. I just use old terminology. Either compressor on or compressor off. So what you're describing, you're saying it's basically normal that it's happening and it isn't an issue. Also, I don't have VCDS. I use third party scantools that pretty much shows me what VCDS shows. What does group 57 show? Also my engine isn't the older FSI, it's TFSI ea 888 gen 2.
Click to expand...
Yes, what I think is happening is a normal action of the ECU, when engine conditions, (cold, idle, etc), mean that the ECU needs to minimise the engine load, so will minimise flow, (A2), or release the compressor clutch, (those with clutch controlled AC). So, no error. Non VAG specific scan tools do not support all VAG specific error codes, so you may not be aware of some current errors.
There will be a VCDS lable file specific to your engine, (FSI), but you'll need the current full version, not Lite.
Mac.
 
Here's the Groups and Blocks that would tell you what's going on.
VAG specific scan tools are not just good for reading fault codes.
They enable you to monitor all of the sensors, (not just the engine), in real time. That's probably more useful than scanning for fault codes, as it enables you to see what is causing them.
Mac.
Screenshot_20230718-174357.png
 
event3horizon said:
I would like to resurrect this thread. @Evripidis, did you ever find out what's wrong? My 2015 Audi A5 is doing the exact same thing, shut off condition 12, mostly during braking at a stop light. But it ONLY does it when the engine is not warmed up, and it's hot as hell inside or outside. The compressor switches off for like 20 seconds, then comes back on. Very small issue, but I'm curious to what it is and hopefully it won't get worse.
Click to expand...
Hi,

Apologies for taking a while to respond.

The compressor ended up seizing up. When this situation was happening it must have been on its way out and what I believe was the case is that; it was giving the engine a bit of a hard time forcing the ecu to switch it off.

It was a replacement used unit but the system had already been contaminated by the previous failed compressor.

To investigate further I hooked up the gauges and noticed what must have been a blockage. I evacuated and the orifice tube was completely caked with black death (contamination/oxidisation/oil/dye paste).

I would start from there because it is easier than trying to figure out the why from VCDS as the sensors/actuators might actually be fine. I spent countless hours debugging the electronic/wiring side of things when a simple gauge check told me all about it.

In the end I removed the "clutch" and kept the compressor as an idler pulley.

Evros
 
Thanks for the update @Evripidis. I didn't expect that. At first it didn't sound like a big problem. From what I can see on my end, my a/c is fantastic, cools down to 40F at vents and no other signs of issues. It was just this thing, where the cool air was turning off for about 10-15 seconds and then it will turn back on. Shut off code 12. Never happens when engine is warmed up, only when engine is 'cold' and car has been sitting in 90-100F weather on the sun.
 
event3horizon said:
Thanks for the update @Evripidis. I didn't expect that. At first it didn't sound like a big problem. From what I can see on my end, my a/c is fantastic, cools down to 40F at vents and no other signs of issues. It was just this thing, where the cool air was turning off for about 10-15 seconds and then it will turn back on. Shut off code 12. Never happens when engine is warmed up, only when engine is 'cold' and car has been sitting in 90-100F weather on the sun.
Click to expand...
Nice to know why though isn't it.
You don't think about the engine load from the AC, but with a cold engine at idle, the AC is the only load, and quite a high load too.
@Evripidis how do you cope without AC? Or are you still engineless?
Mac.
 
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