Volvo: 1990 Volvo 240 aircon switch, capillary tube, aluminum tube

Question
Ray can you help me,
Behind the rotating air conditioning control knob at the console is what looks to be a switch attached on the side of a relay. as you increase the air con setting the relay becomes easier to switch on. at the top of this relay is a hollow aluminum tube approximately 2mm in diameter, this pipe is under pressure. I have broken this tube off the relay box when removing the centre console. what fluid runs through this capillary tube and how does it manipulate the relay? can i bypass this system by using one maybe two switches?

Answer
Tom,
This tube is there to measure the evap temp to keep it from freezing. I am not sure what it is charged with. It is pushed into the evap and not am active part of the A/C system. The only problem I for see is possibly a freeze up of the evap if it is unable to sense temp. If there is sign of evap freezing you need the complete switch.
I would think you could replace the switch with an on/off switch and as you drive be aware of the possibly freezing and turn the system off on cool days to keep from freezing things should work.
There are four wires at the switch so two are for the A/C on/off and the other two are to the control unit to allow for more (higher)idle with A/C on.