hi I have a 2010 skoda superb my issue is cooling fan not running when I select aircon. Had the system regassed this is when he noticed fans not kicking in. With his obd tablet he could run the fans. He was able to check pressure sensor  this was fine . My question is what would stop the fans from starting. Also I live in peterlee county Durham and was wondering if anyone local had a vcds. 

 

Glenn 

 

 

 

There will be a compressor shut down code which will tell you exactly why the aircon is not running, you have not said whether the aircon is cooling, I am assuming not as the reading from the high side pressure sensor is what triggers the fans to run.

 

Did the person check the system pressure static or while cooling?

 

If no codes then there is a possibility of the shear plate having failed or the alloy hub stripped so the compressor shaft is not actually turning.

 

VCDS will tell you all the above.

 

Editted, writing the above prompted me to go and check my system pressures using VCDS, I had recharged my system once a year ago then had to do it a second time and thought there may have been a leak, all looks OK, it was 18°c outside, the static system pressure was 4.7 bar and when the aircon put on full cold & high fan setting it went up to 12.7 bar before stabilising at around 10 bar & 28% cooling fan actuation, evaporator output temperature was about 3° but would have gone colder.

 

I havn't looked at my temperature and pressure charts but the above seems in the right ballpark from memory.

 

This is just to give you an idea of just a tiny bit of what can be monitored on the HVAC control module using VCDS, obviously in my case there were no shut off codes unless I switched the ventilator fan or the AC switch off.

Edited 7 May, 20215 yr by J.R.

Hi pressures were ok. When air con was switched on it worked correctly for about 2 to 3 seconds then shut down. His obd reader could not go into depth like the vcds can but he was able to start both fans these would run until the pressure came down to the correct level. When fans are running the air is cold when they stop its ambient. When I drive down a dual carriage way or at speed the air is cold when aircon is on and not as cold when off. He was happy pressure sensor was working as voltage was changing. But could not figure out the fans were not kicking in. It was if some sensor was not talking to the brain of the car to start the fans. The sensor was checked with engine running and aircon switched on.

Thanks for the reply and any more info would be great.  Also the fellow who did me aircon is going to ask his other aircon contacts if they have had similar issues.

 

Thanks Glenn 

The fans are definitely commanded resulting from the rise in the high side pressure, it can be seen very clearly on a manifold guage set, once it goes above the nominal pressure shown in the charts the fans cut in and the pressure drops & it then cycles with the pressure oscillating around that required.

 

The HVAC control unit must take the input from the pressure sensor and also compare it to the ambient temperature (and no doubt lots of other variables) when deciding what pressure threshold to turn on the fans.

 

I think that VCDS will probably show a compressor shut down code when the fans cut out and the cooling stops.

Thanks for the reply and info really appreciated it, looks like I need vcds to confirm fault code. I will update when fixed.

 

Thanks Glenn 

 

Thanks for the reply and info really appreciated it, looks like I need vcds to confirm fault code. I will update when fixed. So could the fault be with the HVAC unit 

 

Thanks Glenn 

 

Is that a question?

 

If so the answer is I doubt it, when I spoke of the HVAC control unit its because the canbus module in VCDS is called HVAC, it really means the canbus controller node within the Climatronic unit which communicates with the ECU etc and is interrogated via VCDS.

Thanks again for reply definitely looks like I need vcds to pinpoint the fault.