A/C randomly stops working at times...but works fine other times

[4lane]

The other day the AC was working fine and then it suddenly shut off. Another time it wouldn't come on and after 2hrs of driving it suddenly came on for the remaining 2hrs of the 4hr drive. The A/C light never clicks off as in some cases I've read; it always stays on even when it stops working.

Any guesses on what the issue might be? I'm thinking one of these 3 base on scan results below.

1) Compressor Regulating Valve (N280) faulty
- this can be related to the intermittent fault I'm getting under: 00898 - Control Circuit A/C Compressor
2) Refrigerant is low
- doesn't seem plausible since it works fine sometimes??
3) Failing A/C Pressure/Temperature Sensor (G395)
- I have not seen a fault code for this, but it seems to be a common issue

-------------------------------------------------------------------------------
Address 08: Auto HVAC (J255)       Labels: Redir Fail!
   Part No SW: 8T1 820 043 AA    HW: 8T1 820 043 AA
   Component: KLIMA 1 ZONE  H06 0140  
   Revision: A1000000    Serial number: 0106.10.080892
   Coding: 64002000
   Shop #: WSC 06335 000 00000
   VCID: 70E848EFA3B0B4BEAD-8024

3 Faults Found:

00898 - Control Circuit A/C compressor
           008 - Implausible Signal - Intermittent
             Freeze Frame:
                    Fault Status: 00101000
                    Fault Priority: 6
                    Fault Frequency: 1
                    Reset counter: 58
                    Mileage: 162410 km
                    Time Indication: 0
                    Date: 2017.01.26
                    Time: 10:01:47


01273 - Fresh Air Blower (V2) 
            009 - Open or Short to Ground
             Freeze Frame:
                    Fault Status: 01101001
                    Fault Priority: 3
                    Fault Frequency: 80
                    Reset counter: 18
                    Mileage: 162410 km
                    Time Indication: 0
                    Date: 2017.01.26
                    Time: 10:01:47

             Freeze Frame:
                    Temperature: 9.0°C
                    Speed: 0.0 km/h
                    Voltage: 0.00 V
                    Current: 0.000 A
                    Voltage: 12.40 V

01844 - Control Module for Fresh Air Blower (J126) 
            014 - Defective - Intermittent
             Freeze Frame:
                    Fault Status: 00101110
                    Fault Priority: 3
                    Fault Frequency: 41
                    Reset counter: 49
                    Mileage: 162410 km
                    Time Indication: 0
                    Date: 2017.01.26
                    Time: 10:01:47

             Freeze Frame:
                    Temperature: 9.0°C

[4lane]

Last night I ran some more tests. At the time the A/C was working fine. Going through all the tests for flaps/motors seemed to work fine. I cleared this code and ran it for a bit without the code being thrown. I turned the car off/on, ran the tests again and saw this fault thrown again. But the A/C still worked fine. I was kinda hoping to see it stop when the fault was thrown, pointed to N280. Any thoughts and/or what abnormal N280 output tests should look like?

00898 - Control Circuit A/C compressor
           008 - Implausible Signal - Intermittent
             Freeze Frame:
                    Fault Status: 00101000
                    Fault Priority: 6
                    Fault Frequency: 1
                    Reset counter: 58
                    Mileage: 162410 km
                    Time Indication: 0
                    Date: 2017.01.26
                    Time: 10:01:47

[Gunnark100]

If you check your first scan- problem is not ac compressor, but module or v2, but it needs proper diagnose via measure blocks etc!

[4lane]

Another clue to the puzzle: during the times when the A/C is not working, I've noticed that no fans are on to try and cool things down either. I would expect that if the a/c was just not operating, that the rest of the system (blowers, etc.) would be active. Is this true and could this point to something that controls the climate in general? As in, it's not reading the temperature correctly, or is just not operating to be able to read the temp and kick in the a/c, blowers, etc?

Code:
01844 - Control Module for Fresh Air Blower (J126)
014 - Defective - Intermittent
Freeze Frame:
Fault Status: 00101110
Fault Priority: 3
Fault Frequency: 41
Reset counter: 49
Mileage: 162410 km
Time Indication: 0
Date: 2017.01.26
Time: 10:01:47

Freeze Frame:
Temperature: 9.0°C

[bakedziti]

I am not sure about your fans, but sometimes that is the resistor for the blower motor. I have one for sale, if it turns out to be that. I had an issue with my G395 recently, in which the wiring had been pinched. The sensor is just behind the grille on the driver's side, so I suggest double checking the wiring before anything else. My AC wouldn't blow cold at this time, but once the wiring was spliced and reconnected, I am all set.

[4lane]

Ah! Did you get a G395 error when you had that issue? I am not getting that one specifically, but looking at the common issues across the three faults, I see the ones in blue and red below. I wish I could find more info on "TPI 2033596/3". There's nothing that I've been able to find...

00898 - Control Circuit A/C Compressor: Open or Short to Plus
Possible Symptoms
* Climate Control not working
Possible Causes
Fuse(s) faulty
* Wiring and/or Connector(s) from/to Compressor Regulating Valve (N280) faulty
* Compressor Regulating Valve (N280) faulty
* Heating/Climate Control Module (J301) faulty

01273 - Fresh Air Blower (V2)
Possible Causes
* Fresh Air Blower (V2) defective
* Control Module for Fresh Air Blower (J126) defective
* Short of open circuit in wiring to Fresh Air Blower (V2)
* Climatronic Control Module (J255) malfunctioning
Special Notes
* When found in Audi A4/A5/Q5 (8K/8T/8R) models: 
North American Market (NAR) vehicles, see TPI 2033596/3 (or newer)

01844 - Control Module for Fresh Air Blower (J126)
Possible Causes
* Control Module for Fresh Air Blower (J126) defective
* Fresh Air Blower (V2) defective
* Short or open circuit in wiring to Control Module for Fresh Air Blower (J126)
* Climatronic Control Module (J255) malfunctioning
Special Notes
* When found in Audi A4/A5/Q5 (8K/8T/8R) models: 
North American Market (NAR) vehicles, see TPI 2033596/3 (or newer)

I am not sure about your fans, but sometimes that is the resistor for the blower motor. I have one for sale, if it turns out to be that. I had an issue with my G395 recently, in which the wiring had been pinched. The sensor is just behind the grille on the driver's side, so I suggest double checking the wiring before anything else. My AC wouldn't blow cold at this time, but once the wiring was spliced and reconnected, I am all set.

[Gunnark100]

You have all info you need, audi statement with those TPI-s is short, replace one or both! Forget G395, this sensor is integrated to the system with two faults, both wiring and readings, you dont have them!

[4lane]

You think I should replace these two and ignore Compressor Regulating Valve (N280), or which two are you saying to replace?

* Fresh Air Blower (V2)
* Control Module for Fresh Air Blower (J126)

You have all info you need, audi statement with those TPI-s is short, replace one or both! Forget G395, this sensor is integrated to the system with two faults, both wiring and readings, you dont have them!

[4lane]

The only thing that doesn't make sense is when it's not working I can turn the fan up all the way. I would expect it not to blow if it won't blow cool air in the cabin.

However, based on this diagnosis, it does sound like both the blower/control module should be replaced: http://ricksfreeautorepairadvice.com...r-doesnt-work/

I'm going to pull it out and see if I can test it and also clean it up. I've read that the carbon brush dust can cause intermittent issues that a good cleaning will fix.

You have all info you need, audi statement with those TPI-s is short, replace one or both! Forget G395, this sensor is integrated to the system with two faults, both wiring and readings, you dont have them!

[van462]

If you adjust the fan speed it leaves auto mode. The fan speed will always respond to that control. Blower fans do go out on these cars. I have had to pull mine and just clean up the armature and brushes and flush it with alcohol to get all the dust from the brushes wearing. 10 screws hold in the glovebox. If you have AMI in the glove box you will need radio removal keys. You can then see where the blower gets power from the board. A voltmeter lead will slid in next to the connector and you can read the fan voltage. It will change from around 7.5 to 13 volts as you adjust fan speed. If the voltage is changing its your fan. If not then suspect the controller (attached to the blower). Remove the controller (2 screws and the fan twist a few degrees and comes out. You can also take a multimeter set to ohms and check the leads going to the motor, its its open or above 10 ohms then suspect a hung or worn brush. Remove motor to attempt cleaning or just replace it.

[asfastas63]

I had to replace both the blower motor and resistor in my wife's Q5 (which uses the same part numbers) and this sounds like the same problem. I got a new resistor and a used blower motor off ebay.

[Rook518]

Mine was just in for a recall for the AC system. Something with the software not making it blow cold all the time. You might want to check that

[4lane]

Thank you for this. I would be interested to know what that recall was about. If you end up finding out what they did, and/or have the recall notice that would be great. I did not get the recall notification.

Mine was just in for a recall for the AC system. Something with the software not making it blow cold all the time. You might want to check that

[4lane]

UPDATE: I took off the blower which didn't seem particularly dirty, but cleaned it and installed it. I also unplugged the control module, squirted some WD-40 on the the contacts and reinstalled both. A/C worked fine after.

[xl2ealx]

sorry for the old thread reply. Going thru the same thing except i only have the 898 code.

where is the control module that you unplugged?

thanks

[4lane]

sorry for the old thread reply. Going thru the same thing except i only have the 898 code.

where is the control module that you unplugged?

thanks

It's under the glovebox right next to the actual blower fan.