A6 (C6) Avant 2.0 TDI Air Con Compressor Replacement Assistance

[rjsdavis]

Yes, no pressure loss when fitting or removing the sensor.

Thanks. Is it as simply as unbolting the old, and bolting on the new? I am assuming that when a part like this is replaced, it won't need "activating" or "coding" into the computer's ECU or other such nonsense?

[rowdy-999]

Simply unscrews. No coding required.

[rjsdavis]

Right, I obtained a Hella pressure sensor from my local GSF yesterday, and fitted it this afternoon. Interesting side note - using the code "FORUM40" gets you a 40% discount off everything on their website! The sensor was £32.

Spent some time getting the bumper dropped off on the NS corner, and managed to break one of the headlamp washer unions (****!) so all of the washer fluid has now gone...

Anyway - removed the air con pressure sensor. New one on and put everything back together. No difference - air con is exactly as it was before.... (DOUBLE ****).

So, I'm thinking.... Are the reasons for this:

1 - That, after my friend read the G395 code the other day, and cleared it, that it would have reappeared in the ECU immediately after starting the car again to renew it as a "current" fault code? This being the case, does it therefore follow, that I would now need to have the G395 fault code cleared once again, now that the new sensor has been fitted, to effectively enable it?

2 - When Kwik Fit attempted the re-gas the other day and determined that the system wasn't working, would they have then removed all of the refrigerant out of the system before giving me the car back - therefore, preventing the system from working in any event, as there's no bloody refrigerant in the system?

3 - That the pressure sensor simply wasn't the fault, or worse, that the compressor is also at fault too?

Many thanks once again for any useful steers. It's getting warm, and I really, really need to get this fixed!!

[dan2485]

If you had no leaks in the system then there would no requirement for the gas to be removed.

I think that you need to get the code checked again.

The common failure on the sensor is for a plug wire to snap check the wiring to the G395 sensor plug.

When reading fulat codes you must determined when an code is generated if it's due to a failure or is it a sympton of something wrong with what ever the sensor read.

Your Code of G395 - A/C Pressure / Temp Sensor - No Signal / No Communication this means either the sensor is defective (you know that its not) or you have a wiring issue.


read this post.

https://www.vwaudiforum.co.uk/forum/showthread.php/182648-Air-con-G395-sensor-no-vaultage-help-please


If you need the wiring diagram PM me your email address.

[dan2485]

The hyerlinks are not working so copy and paste the post into your brower.

[rjsdavis]

Thanks very much for this post Dan, and for the link to the other thread.

I'm going to lay my hand on a CANBUS cable and a VCDS software set, so that I can get into the car and start looking further. I can't live with myself going up to my friendly LR mechanic and asking him to stick his SnapOn onto the car to clear / read fault codes! This thread will go quiet for a week or two whilst I wait for it to arrive.

Major timing belt service was completed today, but sadly my mechanics code reader wasn't compatible with many of the Audi systems - including air con, otherwise he would have cleared the current G395 code and hopefully that might have sparked the system into life now that the new pressure sensor is fitted

[k6rff]

Hi, just picked this up. I moved to Ludlow 1 year ago so I'm afraid I cannot be of much help. I still have the vcds canbus but I'd recommend owning one of these as it's always useful. Got me through a couple of arguments with Main dealer and was able to prove faults that they denied.

sorry I can't help.

[rjsdavis]

Damn!

Looks like the VCDS map isn't very uptodate :-( You were just a few hundred yards away from me too!

I'd love to have one, but the cost is particularly prohibitive for a genuine Ross-Tech cable.

[k6rff]

Well worth the 245 I paid a few years ago. Over the years that has become money well spent. Gets cheaper every new car.

[rjsdavis]

If you had no leaks in the system then there would no requirement for the gas to be removed.

I think that you need to get the code checked again.

The common failure on the sensor is for a plug wire to snap check the wiring to the G395 sensor plug.

When reading fulat codes you must determined when an code is generated if it's due to a failure or is it a sympton of something wrong with what ever the sensor read.

Your Code of G395 - A/C Pressure / Temp Sensor - No Signal / No Communication this means either the sensor is defective (you know that its not) or you have a wiring issue.


read this post.

https://www.vwaudiforum.co.uk/forum/showthread.php/182648-Air-con-G395-sensor-no-vaultage-help-please


If you need the wiring diagram PM me your email address.

Right, ok. I've now access to VCDS, and I think I'm making a little bit of progress....

1 - The pressure switch has been replaced. I've now been able to remove the DTC with VCDS and it has not returned. I therefore have confidence that the old pressure switch was faulty, and that there are no faults with the wiring. Sadly, this has not cured the problem!

2 - When I first ran the VCDS autoscan, I discovered that there were some other problems shown. Most of them were "voltage related", and I had also had a few occasions where, despite the battery really should have been full, I would find that the car would not even attempt to turnover if the key was left in the ignition for a few minutes whilst the laptop was connected to the car. Completed two battery tests today, and both reckoned the battery was ******. Obtained a brand new Yuasa 5000 900A unit from TPS for £115 and it's in. Car definitely seems to better for it.

3 - Re-ran the VCDS auto-scan. I've some minor problems that need addressing, but I'm still getting:

01858 - Air Outlet Sensor; Right Center (G348)
010 - Open or Short to Plus
Freeze Frame:
Fault Status: 01101010
Fault Priority: 3
Fault Frequency: 1
Reset counter: 167
Mileage: 293066 km
Time Indication: 0
Date: 2017.06.12
Time: 19:16:25

No matter how frequently it's cleared, it returns immediately. Could this stop the A/C system from working?

4 - After sorting the pressure switch issue, I popped into my local Kwik-Fit for a free re-gas attempt. (It's free if it doesn't work and I was quite happy to pay them if it did!!). They confirmed, again, that the system is holding good pressure (VCDS also confirms 5.6bar in the system, so this appears to be accurate), but sadly, it made no difference...

I spent some time with the mechanic, and we could see that:

* The clutch pulley on the compressor is always turning, no matter whether the system is off or on. He wasn't sure, but he thought that it should disengage if the system was off. Is this correct?
* The condensor fan runs when the a/c system is on, and turns off when the system is off - this appears to be correct and working ok.
* The condensor is ok, holding pressure and not leaking

Therefore, based on the diagnosis today - I appear to be back where I started thinking that the compressor (or maybe just the clutch?) is ******?

5 - I've worked out how to more useful data from the VCDS system about the HVAC system that appears to be helpful:

0.650 A A/C Regulating Valve (N280)
64.0 % A/C Regulating Valve (N280)
5.6 bar Refrigerant Circuit Pressure
0.0 Current Shut-Off Condition
12.0 Last Shut-Off Condition
3.0 Last but One Shut-Off Condition
12.0 Last but Two Shut-Off Condition
226.0 Current Value
227.0 Specified Value
31.0 Minimum Position (Lower Stop/Close)
222.0 Maximum Position (Upper Stop/Open)
173.0 Centre Left Vent Sensor (G347)
253.0 Centre Right Vent Sensor (G348)
4.90 V Voltage (5V)
13.60 V Voltage (Terminal 15)
24.0°C Left Vent (G150) Temperature
24.0°C Right Vent (G151) Temperature
Not Occup. Center Vent (G191) Temperature
23.0°C Evaporator (G263) Temperature
20.0°C Air Intake (G89) Temperature
20.0°C Ambient (G17) Temperature
25.0°C Dash Panel (G56) Temperature
25.0°C Dash Panel (G56) Temperature
2940 /min Temp. Sensor Blower Speed
74.0°C Coolant Temperature
ON Idle Speed Increase Request
840 /min Engine Speed
0.0 km/h Vehicle Speed
0.0 Compressor Torque Status
3.5 Nm Compressor Torque
7.0 Air Quality Sensor (G238)
60.0 Fresh/Recirculated Air Request
R.wn.h.OFF Button Status
0.0 Actual Speed Cool. Pump (V50)
0.0 Lower Speed Limit Cool. Pump (V50)
0.0 Upper Speed Limit Cool. Pump (V50)
OFF Coolant Circ. Pump (V50)
5.8 bar Refrigerant Circuit Pressure
129.0°C Refrigerant Temperature
204.0 SW/HW-Version Press./Temp.Sens.
00000010 Status Refrigerant Press./Temp.Sens.

I think that the most useful data is possibly in these last few lines of data:

0.0 Actual Speed Cool. Pump (V50)
0.0 Lower Speed Limit Cool. Pump (V50)
0.0 Upper Speed Limit Cool. Pump (V50)
OFF Coolant Circ. Pump (V50)
5.8 bar Refrigerant Circuit Pressure

At the time of analysing this data, the car was running, and the A/C system was on and running, and set to 16 degrees (it was a warm evening, and the fans were blowing at around 10 or so) - however, if I am reading this correctly, it seems to be saying that the Coolant Circ Pump is "OFF" - is this coolant as in "engine coolant" i.e. keeping the engine from overheating, or does this mean the compressor? Now that I type this, I suspect I've mis-read this, hoping that it was a/c related, and it's actually probably engine coolant related! Gggrrrrr.....

Oh well - I thought it was useful!

Anyway, I am where I am:

* Pressure switch is new
* Pressure switch wiring appears to have no faults
* System pressure is good
* Condensor is not cracked and leaking
* System is full of refrigerant

Surely this means that the compressor/clutch is buggered, and I need to get this replaced? I do have a spare compressor now ready to fit, but before going through the agg of swapping in the new one, is there anything else I should be checking or ruling out before doing this?

Many, many thanks for any help offered... and thanks for the replies thus far!