Need help AC not running.

Dimitar Timev

Dimitar Timev

Member
Hello all.

I have a problem with my air con system. At my local garage the mechanic tested the system for reaks ,and he can't find any Also the system i charged with fresh r134 500grams. But no luck to make it working. We also chek the main cooling fan ,and its working on both speeds.
I have check for errors in hvac system with vag com lite and all is clear.
The mechanick that tested the ac system is suspecting stuck n280 valve.
My question is how and where i can chek with vag com is the ac compresor (n280 valve) reciving the signal to turn on?
I have looked in engine ecu in messuring blocks group 050 and in condition of AC system is OFF ,operationg condition of AC compressor OFF ,but those values are not changing at all even when i press the ECON buton on or off.
So what to do now.. how can i chek the electrical integrity of the AC system ,or is my N280 valve stuck close. But if the valve is stuck close ,were i can chek is the the ecu trying to control it?
 
I think you are right to suspect this N280 valve. The compressor runs all the time, it's driven from the engine, and the N280 controls how much refrigerant is circulated.
More info:

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Mac.
 
Try looking in the HVAC module measuring blocks.
If you added 500g and the system was not previously vacuumed out then there will be too much refrigerant and the system will shut down to protect components.
Why do you think the ECU would control the HVAC?
 
Don't assume that the pressure sensor is working correctly. I had one that indicated zero pressure with a full system. They can be changed without emptying the system. With this fault, the A/C won't work.

RAB
 
Sorry my bad for calling it ECU i mean HVAC control module. I have check the coil on the N280 (12.8 oms). My multimeter says that the N280 is having around 9.9volts on the connector with econ button pressed on.

The system was vacuumed out and then added a fresh 500g r134 freon.

I will post some potos from the HVAC mesuring blocks.
https://imgur.com/KVCrMmo
That absolute pres. 1.0 bar is strange.... If this is coming from the G65 its cleary not correct? I know for the ac compressor to start the pressure inside the system must be min 2.5bar or more. Like i say the system is charged now so it must have that 2.5bar inside or more. If i dissconet the G65 sensor that 1.0bar is still the same. IS THIS A JUST A BAD G65?


Now those two images are again from HVAC mesuring block. They are showing the diffrence betwin econ button on/off.
https://imgur.com/CGEBS4s
https://imgur.com/Ok74aAj

And the last image is from output test on HVAC.
https://imgur.com/lkGeA07
On this image the output test is started and if im correct the main colling fan must start runing? But its cleary NOT runing from that output test.
My local garage mechanic test the fan on/off from his software and it was runing just fine ,but the ac was not working. I don't know way the output test from my vag com is not conroling the main colling fan. Again no error codes in HVAC system ,engine ECU is clear from errors too.

Hope some one can help.
 
Here is more info from ross tech.

Tis’ the HVAC Season

Tis’ the HVAC Season By: DrPeter Intro: In this Tech Tip I will be explaining some quick and easy diagnostic tips for the Volkswagen/Audi HVAC systems. We will be focusing on the systems that are diagnosable with the VCDS scan-tool. Even though the system designs maybe slightly different...
forums.ross-tech.com forums.ross-tech.com
 
The compressor is not controlled by the AC/ECON switch. The compressor runs all the time the engine is running. Many other systems use a clutch to control the compressor, but in the A2, the N280 is the only control. When the ECON mode is selected, the compressor is still running, but the N280 reduces the flow of refrigerant to around 5%.
The N280 is not a simple open or closed valve, it is continuously variable, matching the flow o refrigerant to match the selected cabin temperature. The Rosstech link says :
"... The N280-Refrigerant Regulating Valve activation signal can be checked with an incandescent light bulb in its place. Unplug the N280-Refrigerant Regulating Valve, connect a test bulb to the connector from the HVAC controller and start the vehicle, turn on the AC and watch for the activation command from the HVAC controller. If the bulb lights the HVAC controller is working, and the N280 is suspect... "
Worth trying I think.
Mac
 
Update from this morning.
info from link above:
Here is a list of typical Compressor Shut off codes:
- 0 = Compressor ON
- 1 = Compressor OFF: Refrigerant Pressure too high (> 32 bar)
- 2 = compressor OFF: Basic setting not performed
- 3 = Compressor OFF: Refrigerant Pressure too low (< 2.0 bar)
- 5 = Compressor OFF: Engine Start Detection
- 6 = Compressor OFF: ECON Mode active
- 7 = Compressor OFF: A/C System / FAN OFF
- 8 = Compressor OFF: Outside Temperature too low (< 3.0 °C)
- 10 = Compressor OFF: Vehicle System Voltage too low (< 10.1 V)
- 11 = Compressor OFF: Engine Temperature too high (> 118 °C)
- 12 = Compressor OFF: Shut-Off requested by Engine Control
- 13 = Compressor OFF: Vehicle System Voltage too high (> 17 V)
- 14 = Compressor OFF: Evaporator Temperature too low
- 16 = Compressor OFF: Compressor Activation faulty
- 17 = Compressor OFF: No or implausible Signal Pressure Sensor
- 18 = Compressor OFF: Vehicle Speed Shut-Off
- 19 = Compressor OFF: Shut-Off requested by Central Electronics Control (Load Management)

I loged in vcds and logged on in hvac measuring block 08.
I check the data in group 02 this time with engine running and econ button pressed on. And i get code 3 "- 3 = Compressor OFF: Refrigerant Pressure too low (< 2.0 bar)"
Base on that information i think that the G65 sensor is bad ,or my local mechanic lie that he put 500grams of r134 in the system ,so he can charge me twice.

On monday i will go back to the mechanic garage to see what he will say.
 
To me, it looks like it might be an issue with the pressure sensor. I think it should show much more than 1 bar, assuming a warm/hot day, even with the A/C off (ECON on).

Maybe check the pressures at the service ports at the mechanic's? I would think the high pressure side whould be what the sensor sees, but I might be wrong.

If he said there were no leaks, allowing him to put in new refrigerant, it should not have all leaked out -- not that quickly.
 
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He say no there are no leaks and that he put 500grams in the system. And if thats is correct then the G65 is bad and giving me 3 = Compressor OFF: Refrigerant Pressure too low (< 2.0 bar)".
But like i say i the previous post we see on moday..... Here in Bulgaria everything is possible at the local mechanic :D
 
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! Bara is atmospheric pressure, so either you have a failed sensor or a large leak (or your system wasn't filled). You can change the sensor without emptying the system.

RAB
 
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