Air con problem, gas ok, clutch engages, any ideas ?

[Jonathan]

My aircon is not blowing cold. Initially the compressor was not engaging.

First I checked the pressure on the low side port, measured ok.


Replaced the pressure sensor. Compressor now engages, and stays engaged. But no cold air.


When I turn on the air con and the clutch engages with a clunk, in the cabin there is initially a wooshing gaseous type sound from inside the vents. When the air con worked I never remember hearing this sound (however this is exactly the sound I hear in my wife's car where the air con works a treat ?).


Any ideas, most of what I read about refers to no gas, clutch not engaging and the pressure switch, all those seem ok, what else could be wrong ? Any good next stage diagnostics ?

 

[Luke.]

A blockage? Receiver/dryer need replacing?

 

[Jonathan]

Ok, revisited the gas pressure, in short it didn't have enough. Gave it a good top up and all icy cool now.

Gauge with compressor engaged now reads as shown. Disengaged it is in the middle of the red. (which is how two other good cars were that I checked).

Last regas was 10 years ago following a warranty repair so hopefully it was just 10 years of slow leak. It does make me slightly suspicious that I didn't need a new pressure sensor and that it was just right on the threshold. Having said that the new one triggered with the low charge ?

 

[CRS-Mike]

i got exactly same thing as you from halfords, turns out i over pressured the air con and was lucky not to kill the compressor. i got a lone trader to come sort mine out for 60 quid in the end, he vac'd it and everything its the best it ever been now, not to worry you. (gets any crud out of the system too that can build up into the compressor and f**k it)
these gas things you can buy arnt very good since they can give out a wrong pressure and its not all about pressure either its mainly just the weight in the system from what he and others have told me now.

personally im going to be taking my can bak to halfords and getting the 10 pound back , i suppose the adapter part serves a purpose to check it for pressure tho.

again im not saying its wrong to do it this way, just be cautious of it when its really hot if its not working properly, unbelievably the aircon system can explode in extreme cases taking the engine bay with it! google it bcos it can and has happened to people!

 

[Luke.]

How can 'you' over pressure the aircon?

 

[CRS-Mike]

faulty gauge perhaps, but more often due to over weight. its not really the pressure that is the issue its the amount in there to create the pressure when the temputure rises. i suppose the best time to refill it would be when its 30 degrees Celsius outside since then you get a better'ish readout, but its by no means accurate! weight its the main thing.

 

[Chrisgti6]

Yup, as stated in here it's about weight of refrigerant and lube, not pressure. Pressure is a good indicator that there isn't a leak but not that the correct qty is actually in the system. Recover and refil is best option.

 

[Jonathan]

I read up a fair bit on the pro's and cons of the DIY bottle and its interesting to hear everyones input. On the balance of cost and convenience (and the fact the system had pressure in it) I decided to give the bottle a try. Still working a treat, I will update with any further developments over time.