I have an 87 245 gl with the old style rotary a/c switch. There are four connection points on the back and four connectors. A double green, and a green control the compressor clutch and a red, and a blue-yellow control the idle increase. My switch broke, so I cut the capillary tube and put the idle control and the compressor clutch control into two separate standard switches. That worked fine but then i wanted to have just the rotary switch, so I bought a new rotary switch and hooked it up but it doesn't work. I hooked up the four wires in all the combiantions i could think of but couldn't get it to work. First, what are the correct connections? (two on the back of the switch, top and bottom, and two on the side of the switch, top and bottom) Also does the switch work without the capillary tube connected? What is the tubes funtction? Can I just crimp off the tube and go to a new style rocker switch?
Thanks, Nick

A capillary tube is used to connect the fluid from a remote sensing point to a switch element. If the tube is broken, there can't be any pressure on the switch, so it can't turn on. It would be a plunger or pin in the middle of the switch body. There's no magic here- it's just a sealed copper or brass bulb with a fluid like ammonia in it- something that expands quite a lot with heat. These style switches are used in every home air conditioner, refrigerator, dehumidifier.... they all work the same. You probably can't get it to work without a new capillary assembly. You can probably pull the old bulb out of the goop on the evaporator and get a new one in there, if you can stand working way under the dash for a little while.
Good luck!
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total

Nick -
The Volvo Wiring Diagram Service manual for 1987-88 240 shows what you describe.
There is a microswitch in the circuit that is attached to the rotary switch. Some of the connections are to it, not the rotary switch.

The microswitch connects BL, power from fuse #12, to R, which goes to the a/c relay terminal #61/D+ which, on the relay base, is a double red wire terminal. The other red from that relay base goes to the ECU for idle speed adjustment. The relay is what gives the 10 second delay in a/c engagement after the alternator begins charging.

The two rotary switch terminals have a single green on one, a double green on the other. One of the double green wires goes to the engine bay and thence the pressure sensor on the receiver dryer and thence the compressor clutch. The other of the double green is not shown, but could end up at the heater fan switch terminal #5 via a connector in which it changes to R-W.

The capillary tube has to do with controlling the size of the orifice in the expansion valve. I think it is filled with Freon, and once severed will allow the system to freeze up and damage itself. The 1978 system shows a rocker switch on the panel and a thermostat mounted separately inside the panel somewhere. Same function - keeping the evaporator from freezing over.

What I know about the later models is that I don't know them at all. Some use a variable orifice tube in place of the expansion valve, and there may be some differences in controls.

Good Luck,

Bob

:>)

Go to salvage yard and pull a A/C thermostat...cheap $3 to $5.