Meaning of compressor shut off code

[TheFixer]

This is a long saga,for me and eventually im gonna have to bring my '07 A6 to the shop but my A/C shows a shut off condition of 12. Ive found a definition of the code -----> 12 = Compressor off (shut-off request from Engine Control Module (ECM) via CAN) but what does that actually mean,can I find out more info in diagnostics about it?

Any thoughts appreciated

[Guest 2]

what was it scanned with?

[TheFixer]

Vcds

[Guest 2]

do you have the full fault code?

[gupsterg]

J If a compressor shut-off conditions applies (display group 002) the AC compressor regulating valve -N280 cannot be activated, including during final control diagnosis.
J If no pressure signal is detected by the refrigerant pressure/temperature sender -G395-, the AC compressor regulating valve -N280 must not be activated.
J By way of the signal the Climatronic control unit -J255 calculates the pressure in the refrigerant circuit.
J If the refrigerant circuit is correctly charged, a pressure of 2.6 bar is set at a temperature of -3°C. So that no fault is stored at low temperatures, the Climatronic control unit -J255 only detects a fault in the refrigerant circuit at a pressure below 1.8 bar (set at -12° C). At this temperature the measured value of the refrigerant pressure/temperature sender -G395 is no longer evaluated, however.
J On the Audi A6 a refrigerant pressure/temperature sender -G395 is fitted. It exchanges information with the Climatronic control unit -J255 over the data bus system of the air conditioner LIN bus. Consequently, no high-pressure sender -G65 may be fitted in the Audi A6 (it sends a square signal). So make sure you have the correct part number (the two components cannot always be distinguished by their housings).

Measured value block 002

Display zone 1

Current valid compressor shut-off condition
J Readout = "XX"

Display zone 2

Last compressor shut-off condition
J Readout = "XX"

Display zone 3

Last-but-one compressor shut-off condition
J Readout = "XX"

Display zone 4

Last-but-two compressor shut-off condition
J Readout = "XX"

Breakdown of compressor shut-off conditions
0 Compressor on (no shut-off condition detected.)
1 Compressor off (pressure in refrigerant circuit was or is too high.)
2 Compressoroff (basic setting not performed or not performed without error.)
3 Compressor off (pressure in refrigerant circuit is too low.)
4 Compressor off (engine nor running or has been running for less than 2 sec.)
5 Compressor off (engine speed is below 300/ min.)
6 Compressor off (compressor switched off by ECON118°C.)

12 Compressor off (request from the engine control unit, via data bus.)

13 Compressor off (faulty signal from refrigerant pressure and temperature sender
-G395.)
14 Compressor off (fault in data bus system.)
15 Compressor off (the pressure in the refrigerant circuit in this driving period was at least 30 times too
high.)
16 Compressor off (the measured temperature downstream of the evaporator has for over a minute been below
0°C.)
17 Compressor off (measured temperature downstream of evaporator below -5°C.)
18 Compressor off (there is no valid measured value for theambient temperature, possibly both
ambient temperature sensors -G17 and fresh air blower intake duct -G89 defective.)
19 Compressor off (-Climatronic control unit -J255
was switched on via the "auxiliary heater" function.)
20 Compressor off (readout currently vacant)
21 Compressor off (measured ambient temperature wasbelow -8°C and is still below
-5°C, there is no request for automatic recirculated air mode or the measuredambient temperature
was below +2°C and is still below +5°Cand the "automatic recirculated air mode" function is not
active.)
22 Compressor off (measured passenger compartment temperature below +8°C. The measured
ambient temperaturewas below -8°C and isstill below -5°C. Arequest for
recirculated air mode has been received.)
23 Compressor off (via the data bus system a fault message for activation of the
radiator fans was sent, e.g. by therelevant engine control unit,and received bythe
Climatronic control unit -J255.)
24 Compressor off (readout currently not used.)
25 Compressor off (readout currently not used.)

Ref:- Audi Portal: Actuators Diagnostic . Audi A6 4F (2005- ). N280

AC compressor regulating valve -N280

*** view image in above link ***

A and B - Connector of AC compressor regulating valve -N280 -N280

The electric AC compressor regulating valve -N280 is pushed into the compressor and is secured by a spring ring.
It forms the interface between the low, high and crankcase pressure in the compressor and is the precondition for clutchless operation.
The adjustment of the swash plate is effected by these different pressures.
That means, if a higher cooling power is required, for example, the regulating valve is activated by the Climatronic control unit -J255.
A pulse width modulated voltage signal moves the plunger in the regulating valve. The duration of the applied voltage determines the adjustment travel.
The adjustment alters the opening cross-section between the high pressure and the pressure in the crankcase of the compressor. The crankcase pressure increases and, by way of the piston stroke, effects a greater skew of the swash plate.

K Notes:
J If an inadequate vehicle voltage is applied, faults may occur in the air conditioning system, or it may fail altogether.

J If the regulating valve fails, the wash plate positions itself perpendicular to the longitudinal axis of the compressor such that the cooling function is disabled.

A Air conditioner; Rep.Gr. 87; Checking switch-on signal for AC compressor regulating valve -N280
A Current flow diagram; ELSA

Ref:- Audi Portal: Actuators Diagnostic . Audi A6 4F (2005- ). N280

Checking AC compressor regulating valve -N280

*** view image in above link ***

The illustration shows a signal with a ratio of approx. 80%.
The pulse width -A- is dependent on desired refrigerant output, the vehicle electrical system voltage etc. (the current is regulated by the Climatronic control unit -J255- via the AC compressor regulating valve -N280- across the range -A-).
The signal interval -B- is always 2 milliseconds (corresponding to a frequency of 500 Hertz).
The signal ratio is produced from the ratio between the pulse width -A- and signal interval -B-.

Your post:-

So I'm finally getting back onto this,here is some HVAC stats.Still no fault codes

5.6 bar Refrigerant Circuit Pressure 21.0°C Evaporator (G263) Temperature
20.0°C Air Intake (G89) Temperature
17.0°C Ambient (G17) Temperature
24.0°C Dash Panel (G56) Temperature
2880 /min Temp. Sensor Blower Speed
71.0°C Coolant Temperature
0.0 Compressor Torque Status
3.0 Nm Compressor Torque
5.6 bar Refrigerant Circuit Pressure
16.0°C Refrigerant Temperature

Im going to get the air/con serviced just to rule that out......

From:- Air Con Not Working - Page 3

[TheFixer]

The HVAC itself gives no fault code but here some data I gathered today.

0.650 A A/C Regulating Valve (N280)
63.5 % A/C Regulating Valve (N280)
0.0 Current Shut-Off Condition
12.0 Last Shut-Off Condition
23.0°C Left Vent (G150) Temperature
23.0°C Right Vent (G151) Temperature
Not Occup. Center Vent (G191) Temperature
22.0°C Evaporator (G263) Temperature
19.0°C Air Intake (G89) Temperature
15.0°C Ambient (G17) Temperature
22.0°C Dash Panel (G56) Temperature
2820 /min Temp. Sensor Blower Speed

0 (zero) is compressor on i think, but my system will not blow cold air. Had gas checked but was ok.

Just thinking is 12 just meaning that when I turn off the ignition the ECM is sending the off request to turn off the compressor? Thus showing a 12 for compressor condition?

[gupsterg]

Measured value block 002

Display zone 1

Current valid compressor shut-off condition
J Readout = "XX"

Display zone 2

Last compressor shut-off condition
J Readout = "XX"

Display zone 3

Last-but-one compressor shut-off condition
J Readout = "XX"

Display zone 4

Last-but-two compressor shut-off condition
J Readout = "XX"

Which display zone data from??

[TheFixer]

VCDS.jpg
Is this what you mean?

[gupsterg]

YEP.... thank you for screen shot... I will check mine and post screenie...

I was digging around to see part no for N280 valve and found none...

Then searched web and seems as if valve is only available with compressor...

Something for you to read Link:- a/c not cooling

Just thinking is 12 just meaning that when I turn off the ignition the ECM is sending the off request to turn off the compressor? Thus showing a 12 for compressor condition?

My car before car started... note code 6 as ECO button had been on... you are correct about code 12...



My car started... with temp set on AC as 19... outside temp on DIS 17...



My car started... with temp on lowest AC setting "LO"....



If you look at MVB's 001 (Group 001) when car not started/AC off, you can see N280 is 0.0A, 0%



Then as car started and AC on temp"19"... A=AMPS go up... AC reg valve work...



Then as AC temp lowered... AC working more... AMPS used go up... AC reg valve % climb...



Please check MVB/group 001... post results...

Another one which maybe good to check...

Measured value block 011

Front cold air flap control motor -V197

Display zone 1

Actual feedback value ofcold air flap control motor potentiometer -G315 (specification "10 ... 250").

Display zone 2

Specified feedback value of(specification "6 ... 254").

Display zone 3

Learned feedback value ofcold air flap control motor potentiometer -G315 at lower limit (cold air flap closedspecification "10 ... 70").

Display zone 4

Learned feedback value of cold air flap control motor potentiometer -G315 at upper limit (cold air flap open, specification "200 ... 250").

Ref Link 1:- Audi Portal: ECU Diagnostic . Audi A6 4F (2005- ) . Climatronic J255

Ref Link 2:- Audi Portal: ECU Diagnostic . Audi A6 4F (2005- ) . Climatronic J255

Ref Link 3:- Audi Portal: ECU Diagnostic . Audi A6 4F (2005- ) . Climatronic J255

Ref Link 4:- Audi Portal: ECU Diagnostic . Audi A6 4F (2005- ) . Climatronic J255

[TheFixer]

Thanks!!!

I checked your screen shot figures against my car with the same temp settings. Only value with no change is the refrigerant pressure.It reads 4.4Bar no matter what setting. The amps and valve percentage values change in line with what you have shown me.

I should get to check those other things later but kids have me busy at the moment lol

Could the Refrigerant pressure/temperature sender -G395 be the issue?