A/C Working Now, Finally...

Hi all. Today I got the air-conditioning system working again, yeah after years of idling. Last Saturday, I went to a local air-condition shop here, they seem clueless when the compressor clutch keeps on on and off by itself rapidly. For local cars, that symptoms always related to defective switch or relays, which the local boys do not know where and which is it for Volvo! I then told them to let me get back and study the system first!



Did some revision from VADIS and I do understand, there is a pressure switched also called as pressostat attached as shown in below picture. The mechanism is very simple, it will cut the compressor off when the pressure is getting low, this is to avoid icing as per my reading. The next morning, I turned-on the a/c and short the switch off (remove the socket from the switch and short both terminals). This bypasses the pressure switch and compressor engaged.



With that knowledge, I went to the same workshop again. There is another assistant which seems more competent than the other mechanics there. I explained the concept of pressostat and he understood. What we did today are as below;

1) Release out all old refrigerant inside the system. It was read around 60 (psi) if I am not mistaken, which regarding to the a/c guy, that is too high. Perhaps because of the gas expansion due to long sitting inside the system. Therefore, pressostat disable compressor on both conditions, over-pressure and low-pressure; it need the optimum pressure level only.

2) Using a vacuum pump, a suction made to remove any air pockets or residues insisde the system.


3) Short the pressostat terminals, start topping-up with new refrigerant until 30 (psi). The a/c started blowing off cold air.


4) Re-install the pressostat, and it works! It allow the compressor to turn on and off accordingly. One way to test it instantly is to rev-up the engine, higher revolution dropped the a/c system pressure down and this will be sensed by the pressostat which then cut-off suplly to the compressor magnetic clutch; it works!

And now the car is really cool; freezing! Cheap solutions, easy fix, given that you know what you are doing. This project really makes me learn new things!

Good Day all!