Evening folks 

 

On my new to me 2006 Octavia diesel estate I noticed the air con didn't blow cold and assumed it needed a re-gas. It's the dual climate contro version. 

 

I noticed on further playing with it that I only seem to get hot air if it's turned right up to high?! 

 

The fans work fine and direct sir accordingly. I did the reset thing by holding the two button which hasn't made any difference. 

 

Could it just need a re-gas? Read some horror stories that it could be head gasket related (although drives fine and no mayo under the oil cap etc) 

 

Many thanks for any help! 

 

 

 

 

 

Hi, 

 

Looks like your N280 valve has gone, get someone with VDCS to confirm, shame your not closer wold have done it for you.

 

Had same on mine 6 years ago, new compressor and condensor later all good, did it myself, save £1000!!!!!

 

 

Trevor

On 24/06/2022 at 23:18, Aston_Bodger said:

Hi, 

 

Looks like your N280 valve has gone, get someone with VDCS to confirm, shame your not closer wold have done it for you.

 

Had same on mine 6 years ago, new compressor and condensor later all good, did it myself, save £1000!!!!!

 

 

Trevor

what is shown on VCDS if it has gone?

 

mine doesn’t have any error codes and values look fine according to the garage. 

Nothing, do not rely on a garage to use their grey matter or logic to diagnose.

 

If VCDS shows the resting high side pressure as correct for the ambient temperature and  modulating valve engaged at 100% but the high side pressure does not rise and evaporator temperature does not fall then it will either be the N280 modulating valve, a broken shear plate or stripped splines on the hub.

 

Or the auxiliary drive belt could be missing but you would have battery problems in that case.

1 hour ago, SiW80 said:

what is shown on VCDS if it has gone?

 

mine doesn’t have any error codes and values look fine according to the garage. 

Mine was showing it was working fine, look in the shut off codes, should be 0.0 if ok, mine was, but all I got was hot air from the A/C.

Where are you?, if your close to Milton Keynes, I will have a look for you.

 

Trevor

You could have acquired two issues.

 

The first is the common A/C compressor N280 valve issue causing loss of cooling.  They are a cheap part to buy, even cheaper to clean (see videos on the Tube) and an easy DIY job but the refrigerant gas handling is the expensive part of the operation best left to a professional.  They fail due to poor design which can clog easily if the system becomes contaminated for some reason e.g. pump wear, debris from a holed condenser, this is compounded by the valve being commanded open by a PWM voltage which initially gradually increases instead of instantly going from 0 to 12V.  Redesigned aftermarket valves available.

 

However it may just require a re-gas.

 

The second with hot air.  If you are getting satisfactory hot air (~60C) at the vents at HI setting but otherwise poor heating you could have a dodgy cabin temperature sensor (pencil eraser size part in centre of fan control knob), this could also influence A/C performance.  If even at HI the temperature at the vents is unsatisfactory you could have a clogged heater core, bad thermostat.

 

Because everything is electronic it is essential that you have the car connected to diagnostic equipment to see what all the various sensors are showing, only then can you say with a degree of certainty where the problem(s) lie and how best to confirm and rectify the diagnosis.

 

You cannot make diagnostic assumptions based on old-skool mechanical logic when dealing with modern cars as there's always a sensor, wiring and controller that's involved.

 

A quick and dirty test you could try for A/C, set to LO and monitor vent temperature for a couple of minutes then hold something hot in front of the cabin temperature sensor and see if it blows any cooler.  By using the car's cigarette lighter for this I found my A/C improved, a bad solder joint on the sensor caused improper sensing.  Again having diagnostic equipment will give an overview of your car's sensors' readings, sensors need not be faulty with oxidation and vibration of connectors a factor to consider.

 

For the heating side, with the car's engine up to temperature have a feel down in the passenger footwell, at the front where the vertical panel meets the centre section.  You should just be able to touch the aluminium heater core inlet/outlet pipes, if they are unbearably hot you SHOULD be okay in that area so again look into what the car is sensing and what it's doing about it.

 

These are just some possible scenarios to consider and it may be worth looking for a professional that offers a free A/C diagnosis, no fix-no fee type of deal.

 

 

Edited 26 June, 20223 yr by MicMac

I get cold air then warmer and colder again in a cycle. 
 

My VAG specialist checked it so I trust them more than the dealership or a general garage.