Hi,

 

My AC doesn't work. Checked codes with VCDS, found 'Air qualioty sensor' fault, so replace it and cleared error - not resurfaced after change, so assume this is now fine, but AC still won't blow cold air..

As I need car on daily basis was thinking about popping to a workshop to check solution pressure in system, but my situation prevents me from going there before 4PM.

 

So my questoion is - how long does it take to get that checked in workshop - will I be able to book a visit to assess situation in time between 4PM and closing time for workshops??   And what that involves - just placing sensor over valve or something more complex??  

I would then make decision on further steps..

Normally it would be connected to a machine that evacuates all the gas and this is checked against the correct weight of gas from the sticker on the slam panel. The machine then draws vacuum on the cars ac system and sits for around 1/2 hour to check for leaks. The machine then cleans the gas that was removed and adds the correct amount of oil and then refills the car system with the correct weight of gas. All in all should be done in an hour or so, unless faults are found.

Edited 30 August, 20214 yr by Kenny R

You can read (with VCDS  in minutes) the pressure read by sensor G65 in one of the measuring blocks of the HVAC module. 

Do so at ambient temperature with ignition on, engine off, engine/bay all at ambient temperature.

Edited 30 August, 20214 yr by Wino

Then compare that pressure against a chart for R134a with low side pressure against temperature, also check whether the VCDS reading is guage pressure or absolute pressure, I have a feeling that its the latter but can never recall, Wino knows as he posesses a memory, something I am very jealous of him for

 

Also check for a compressor shut down code in VCDS, I think zero means there is not one & the system should be operating, again Wino can confirm.

 

If there is no shut down code (low pressure is one of them) then its likely your fault is a sticking modulating valve, a broken shear plate or stripped splines on the drive hub.

Despite Ross-Tech themselves talking about VCDS reading absolute pressure, I have reason to believe it is based on a misreading of some VW group published info, and has no basis in fact.  Empty systems (or sensors in open air) read 0.0 bar in my experience, which they would not if sensor G65 read absolute pressure (they'd say 1.0).

 

A compressor shutdown code of 0 means it has not been actively shut down.

 

 

If you do take it to a garage, checking high and low side pressures with system running should take a matter of minutes (single figures) and involve only connecting a gauge set to the two ports.