AC blowing ambient air

[hiwasss]

The AC is not blowing cold air and I got the following fault from OBDEleven. I was able to clear the code but it's still not blowing cold air. Would anyone have a suggestion on where to start? I put in a new battery for a month or two and cold air has been working until today.

8 Air Conditioning

*** System description: KLIMA 3 ZONEN
*** Software number: 8T1820043AQ
*** Software version: 0180
*** Hardware number: 8T1820043AQ
*** Hardware version: H08
*** Serial number: 01211020110439
*** Long coding: 66102000

*** Trouble codes:
******* 01206 - Signal for duration of -Ignition OFF- Implausible signal
*********** Intermittent
*************** Priority:* 7
*************** Frequency counter:* 2
*************** Driving cycle: 59
*************** Mileage: 194014 km
*************** Date: 2010-01-22 00:21:51
******* 00446 - Function limitation due to insufficient voltage
*********** Intermittent
*************** Priority:* 2
*************** Frequency counter:* 2
*************** Driving cycle: 56
*************** Mileage: 193768 km
*************** Date: 2021-03-18 12:33:31
******* 00457 - Vehicle Electrical System Control Module Please read DTC
*********** static
*************** Priority:* 6
*************** Frequency counter:* 1
*************** Driving cycle: 40
*************** Mileage: 195364 km
*************** Date: 2021-04-30 13:30:13
******* 00256 - Sensor for refrigerant pressure/temperature Implausible signal
*********** static
*************** Priority:* 7
*************** Frequency counter:* 1
*************** Driving cycle: 40
*************** Mileage: 195364 km
*************** Date: 2021-04-30 13:30:13

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[Audibot]

******* 00256 - Sensor for refrigerant pressure/temperature Implausible signal
*********** static
*************** Priority:* 7
*************** Frequency counter:* 1
*************** Driving cycle: 40
*************** Mileage: 195364 km
*************** Date: 2021-04-30 13:30:13

This is quite telling about your problem right there. Your refrigerant pressure sensor (located on the condenser somewhere) may have gone bad. It may also indicate that you've lost pressure in the a/c system, although if it was still good, it should tell you another error message.

If you can get into the HVAC module, into the measurands, and see if it gives you reading when you turn on the a/c (you should see a pretty high number, in bars). If it reads somewhere between 3 and 30 bars, I'd say your system isn't turning on. And obviously if there is no reading, the switch is bad and you need to replace it.

[Midnight_Rider]

When was the last time you charge it?

[hiwasss]

When was the last time you charge it?

I haven't recharged the freon at all, car is MY 2012. I'll give that a try to see if thats the problem.

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[coop3422]

Curious what resolves your problem. I bought my 2015 S4 last summer, it must have been a cool day, or the AC worked at the time of test drive. But when I picked it up a few weeks later, no AC. Had Audi charge it, still nothing. Paid them an hour to inspect it, they found nothing and said they got no codes, so recommended changing the AC compressor for ~$3,800 CAD. Scanned it w/ OBDeleven and found the 00256 code as well.

I bought a sensor that goes near the front of the car behind the bumper. Some had luck with that solving the problem, but I wasn't lucky, I don't think so anyway. After I got my car back from Audi, when you press the AC button, it will illuminate, but goes out as soon as you let go. It did this when I first got the car and when my Indy tried to charge it (his software wouldn't work, which was why I went to Audi), it would then stay illuminated. I know it's not going to happen, but I'm hoping the sensor I replaced was the issue and once the AC light will stay on, I'll get cold air. But I'm not usually lucky like this, so I'm expecting to be out $3k for a new AC compressor.

Really curious what you find out.

[Shane Horning]

Curious what resolves your problem. I bought my 2015 S4 last summer, it must have been a cool day, or the AC worked at the time of test drive. But when I picked it up a few weeks later, no AC. Had Audi charge it, still nothing. Paid them an hour to inspect it, they found nothing and said they got no codes, so recommended changing the AC compressor for ~$3,800 CAD. Scanned it w/ OBDeleven and found the 00256 code as well.

I bought a sensor that goes near the front of the car behind the bumper. Some had luck with that solving the problem, but I wasn't lucky, I don't think so anyway. After I got my car back from Audi, when you press the AC button, it will illuminate, but goes out as soon as you let go. It did this when I first got the car and when my Indy tried to charge it (his software wouldn't work, which was why I went to Audi), it would then stay illuminated. I know it's not going to happen, but I'm hoping the sensor I replaced was the issue and once the AC light will stay on, I'll get cold air. But I'm not usually lucky like this, so I'm expecting to be out $3k for a new AC compressor.

Really curious what you find out.

I wouldn't pay 3k for an ac compressor. They are super easy to change.

[coop3422]

I wouldn't pay 3k for an ac compressor. They are super easy to change.

Are they? I had a thread about it last summer/fall, but didn't get much traction on here.

[Shane Horning]

Are they? I had a thread about it last summer/fall, but didn't get much traction on here.

Well yes very easy to change if you have the tools. I'm not sure how expensive they are but I would think a good used one could be purchased for reasonable

[coop3422]

Well yes very easy to change if you have the tools. I'm not sure how expensive they are but I would think a good used one could be purchased for reasonable

I did a bunch of research last year and found new OEM (Bosche I think?) for around $650 USD. I'm fine with that, it's the crazy labor that kills me.

[hiwasss]

This is quite telling about your problem right there. Your refrigerant pressure sensor (located on the condenser somewhere) may have gone bad. It may also indicate that you've lost pressure in the a/c system, although if it was still good, it should tell you another error message.

If you can get into the HVAC module, into the measurands, and see if it gives you reading when you turn on the a/c (you should see a pretty high number, in bars). If it reads somewhere between 3 and 30 bars, I'd say your system isn't turning on. And obviously if there is no reading, the switch is bad and you need to replace it.

Are you referring to the G395 sensor (4H0959126A) near the driver's side front bumper?

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[coop3422]

Are you referring to the G395 sensor (4H0959126A) near the driver's side front bumper?

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Have you replaced that sensor yet? I did, but no luck. I have one last think you try before confirming that didn't fix it, but don't feel lucky about my chances.

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[hiwasss]

Have you replaced that sensor yet? I did, but no luck. I have one last think you try before confirming that didn't fix it, but don't feel lucky about my chances.

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I have not, just confirming thats the right part. They go for between $20-$50 so not a big loss if it doesn't work out.

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[coop3422]

I have not, just confirming thats the right part. They go for between $20-$50 so not a big loss if it doesn't work out.

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Not sure what it is in the US, but I paid $130 CAD from the dealership for mine. Also if you do replace yours, make sure you get the O ring took. The parts guy didn't mention it so I had to drive across the city to get the sensor, and again the next day for the O ring.

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[Shane Horning]

I did a bunch of research last year and found new OEM (Bosche I think?) for around $650 USD. I'm fine with that, it's the crazy labor that kills me.

Ok I just got done changing the compressor on a customers b8.5 a4. Took me 30 min . Did everything from the top. Only thing I removed was intercooler pipe going to throttle body. Very easy all you need it 16mm wrench to remove the belt,13mm socket to remove the 3 bolts holding compressor and t45 to remove ac lines

[coop3422]

Ok I just got done changing the compressor on a customers b8.5 a4. Took me 30 min . Did everything from the top. Only thing I removed was intercooler pipe going to throttle body. Very easy all you need it 16mm wrench to remove the belt,13mm socket to remove the 3 bolts holding compressor and t45 to remove ac lines

I'm assuming the job is significantly more work with the 3.0T?!

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[Shane Horning]

I'm assuming the job is significantly more work with the 3.0T?!

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Shouldn't be much harder actually although you will need to work at it from the bottom

[hiwasss]

Not sure what it is in the US, but I paid $130 CAD from the dealership for mine. Also if you do replace yours, make sure you get the O ring took. The parts guy didn't mention it so I had to drive across the city to get the sensor, and again the next day for the O ring.

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Is it absolutely necessary that the front bumper has to come off to access the sensor/switch?

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[coop3422]

Is it absolutely necessary that the front bumper has to come off to access the sensor/switch?

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Not at all. Pop the hood and shine a light down the passenger side behind the bumper. You'll see it, definitely don't need to remove the bumper.

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[hiwasss]

Not at all. Pop the hood and shine a light down the passenger side behind the bumper. You'll see it, definitely don't need to remove the bumper.

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Passenger or driver's side, all pics indicate driver.

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[coop3422]

Passenger or driver's side, all pics indicate driver.

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Sorry it's drivers side I even said that earlier in this thread. Must have been tired last night lol.

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[hiwasss]

Sorry it's drivers side I even said that earlier in this thread. Must have been tired last night lol.

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Finally had a chance to install the new sensor and it worked. So glad that I spent less than $40 (sensor and 24mm deep socket)to get cold air again. I bought the Keenso 4H0959126B sensor since it was the quickest to be delivered.

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[coop3422]

Finally had a chance to install the new sensor and it worked. So glad that I spent less than $40 (sensor and 24mm deep socket)to get cold air again. I bought the Keenso 4H0959126B sensor since it was the quickest to be delivered.

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I've gotta take my car to my Indy, and have him do whatever he did last time to make the AC light stay illuminated. I'm hoping the sensor fixed my issue, but just been able to check because Audi made it not stay on after saying I needed a new compressor.

Glad it worked for ya!

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