Question:
I have just traded in my old 1983 240 GLE on a 1997 V70 and it is
interesting to see how the technology has changed. One thing that
troubles me is the efficiency of the air-conditioning in the newer
model
But in the newer model (without climate control) this thermostat
control appears to have been lost. If it gets too cold but you still
want to run the system you reach for the cold/hot dial and turn it
up. This does not appear to result in the air-conditioning being
disengaged (I can still hear it engaging, even when I turn the dial to
the hottest setting), rather hot air is just introduced. To me this is
just a waste of fuel as you are running the compressor when not
required (simply to compete with hot engine heated air). Is there
something wrong with my car or is this the way it works nowadays?
Answer:
It has to do with the design of the system. The A/C on your '83 used an
expansion valve, and with this type of system, an evaporator temperature
sensor can be used, and it can be made adjustable. On the 700 series
and all later Volvos (and the last 2 years of 240), the A/C system
relies on a fixed orifice (this design is called Cycling clutch orifice
tube or CCOT) for expansion, and with this type really can only run at
full power, so you have to add heat if you don't need the full cooling
effect, which will waste some fuel. Unfortunately, that's the way it
is. If you add complicated (electronic) climate control, then the A/C
can be cycled on and off based on interior and duct temperature as well.
