Hi All, I have had a problem with my daughters Air Conditioning on her mk1 Fabia 2002 TDi Elegance, it stopped working ! , scanned it with VCDS and it showed evap sensor intermittent, so I tried replacing the thermistor only with a standard part from RS and it didn't work ! so I ordered the part 6RD907543 and fitted it the other day (fairly hard access) and the air con started working, but not very well in cooling, so I tried one of the refill bottles from Halfords which I must admit was a nearly empty bottle, anyway I think some must have gone in as it had slightly cooler air. So monitoring the air con values with VCDS it was showing the pressure as 7.0 bar to start with and after the small topup 7.5 bar is that correct or should it be more ? cheers Stuart

You don't mention what conditions you are measuring under, so hard to say.  Best bet is a long time after engine has last run, so everything in the car at same, ambient temperature; engine off, ignition on.

 

See here, under heading in red "Added information 12 July 2016". Note test conditions: "When key is on, engine is off, static system pressure"

 

 

 

 

 

 

 

 

 

 

 

 

Edited 4 August, 20178 yr by Wino

Hi Wino, the engine was running with the air con switched on and I added some r134 with it running, I will click on the link and have a read, cheers Stuart

Yes the engine off static or standing pressure will only give you an idea if anything is left in there as it will reflect the fluid's saturation pressure at the ambient temperature.

With the engine running, fan on full speed air vents open and lowest temperature selected, you should see 25>35PSI on the low side and maybe 7C eventually at the centre vent.

 

So, you will need a some more R134a in there to get the low side of that system up to 1.7Bar(g) to 2.4Bar(g).

 

VCDS will only be reading the hi side pressure from the pressure sensor and that should be 8.6Bar(g) to 10.0Bar(g) from what I've seen.

 

Does your Halford's can connector not come with a pressure gauge on it so that you can watch what is happening as you load it in?

 

Edit:- one thing that I do know is, as you, as you should do, only charge with gas, the temperature in your small tin of R134a will drop as will its pressure, you now need to heat it back up or the system will not draw/suck that new charge in, I have got to that stage with daughter's late 2009 Ibiza, I'll need to get back to that job sometime and complete that recharge, though I got the vent temperature down to 8.4C, but still space for more R134a in there! (in the industrial fridge sorting world, heater bands are used to "liven" up the charging cylinder.

Edited 5 August, 20178 yr by rum4mo

OK thanks for that rum4mo, yes there is a gauge on the trigger can and from what I remember it was reading at the bottom of the green area, and like you say the bottle was cold at the bottom, according to VCDS the centre vent temp went from 15c to 13c after the small topup, so am I doing it right trying to top it up with the air con running or when the ign is on but engine not running with air con switched on ? cheers Stuart

You are meant to top up a fridge system with the system operating, so what you are doing is okay. 

 

The only time that you load up a fridge system with power removed, is after that system has been evacuated and so is under a vacuum, if you tried running most fridge systems with a vacuum inside initially, and then started to load a gas charge in, one of two thing would happen, the first is "nothing" pressure switches would inhibit the operation of that system, the second, if all system protection was removed and the system was able to operate, then with bigger systems with electric compressors, damage would occur. So, bringing an evacuated fridge system back into service begins with starting to load the charge in with it in a power off condition, then after the charge stops flowing into the system, power gets enabled and as any protection devices will now be enabled, charging continues until the correct weight of refrigerant has been loaded into the system in the case of critically charged small systems, ie auto HVAC, or in bigger systems, until the running pressures "look good" for the ambient and load conditions.