How to diagnose air con problems

[PND]

Well, yet another car with air con not blowing cold.. 

Is there a set of tests I can do to try and diagnose what's wrong?  For instance, what are the symptoms of just needing a re-gas rather than needing a new compressor?!?    I've read all your posts about leaks, switches, compressors, etc.. but I'm not really sure what I should be looking for.  Does the 'cooling' function work independently from the 'heating' function for example?  Car is 5½ years old. 

Anyone give me some good pointers? Would you recommend an air con specialist rather than main dealer?  I want to get it sorted in time for the scorching summer we're about to have!!

Cheers in advance for all the helpful suggestions you're about to reply with... 

Paul.

[Drapoon]

I'll talk you through my experiences and hope it helps

My air con packed up (07' gti) and I instantly thought compressor however it turned out to be the valve instead and a £120 fix which I managed to get for £60 with a 50% contribution from vw.

You will need a aircon re-gas with an added dye to see if & what's leaking then take it from there. If your compressor is a zexcel (sp) branded unit as opposed to sanden then there's a good chance that's failed. I recall you can identify which unit you have by the visual differences in the belt driven end (search t'internet for this info)

My advice would be go to a vw dealership as they are a known fault & if you play your cards right & promise to service your car there next time they will get you a 50% contribution sorted from Vw. If you are anywhere near Bedford then the Vindis dealership there are mod friendly and sorted me out a treat!

[PND]

Hi Drapoon - thanks for the reply and advice. 

Is there anything I can try to work out how knackered it is?  For instance if I've got the temp is set to 'low', what difference should pressing the 'econ' button make?  It doesn't seem to make any difference at all at the moment..

I just want to try and eliminate anything I can before I go to the dealers/specialist so I don't get told a load of tosh!

Suggestions please.. 

[stealthwolf]

On the older models, AC is turned on by default and the ECONomy button turns off the aircon. On later cars, this was changed to the AC button - simple on/off.

[PND]

I assume I should be able to hear a difference then when the 'econ' button is pressed?  The fans speed up when I turn the temp down to 'low' but just doesn't get cold.  Does it sound like the dreaded compressor, or just a lack of gas?

[mortygttdi]

Your best bet is to get it on VCDS has it can tell you if the compressor pulley is turning at what rpm and also if there is any faults with the air con? usually it will come up with refrigerant pressure too low if it just needs a re gas.

Darren

[PND]

Cheers Darren.. looks like I might have to pop over at some point then! 

[gigolo456]

Hi there, just to confirm, when the Economy button is on and lit up, the aircon is off and when the light is off, the aircon is on, and i know when it's on because the vents crackle a bit and the car is a bit jumpy, does anyone else have this when the aircon is on?? My car is a 2005 GTi...


Andrew

[mortygttdi]

Stop doubting yourself Andy, your Air con is fine mate, mine does exactly the same has do most cars when the compressor is running.

Darren

[gigolo456]

Oh it works alright Darren, it blows cold (touch wood), just ensuring the poster of this thread knew the difference in the function of the Econ, lol!! As for the Auto, i never have that on, goodness knows what that's for!?

[PND]

Hi - yes I know what the 'econ' is for, I just can't remember what used to happen if I pressed it!