Originally posted by ALBundy@Mar 22 2005, 10:14 AM
The E46 and E39 have a more advanced system. Well, if you are familiar with the term variable speed compressor. What traditional compressor does is, when the interior temperature reaches, say the temperature set by you, the magnetic clutch will disengage and hence the compressor won't be running, and when the temperature increases, the clutch would be re-engaged, in layman's term cut in - cut out. Plenty of wear and tear!! That's why I always set my temperature pretty cold so the compressor doesnt cut in/out often.
As mentioned earlier, the system in the E39/E46 is more advanced. The compressor actually runs all the time but the rotation speed varies depending on the load, once the interior is cooled, the compressor will run at low speed and vice versa. This actually prolongs their lifespan.
Hope this helps!
Al
sorry , but thats not correct.
there has never been anything like a 'variable speed compressor'.
what there is on most conti cars is a compressor that is 'on' all the
time , ie , it does not cut in/out depending on temperature , like most
Jap aircon systems.
How the system modulates temperature (and by definition , how hard
the compressor works) is by having an 'expansion valve' that has an
adjustable aperture. The aperture is controlled by the thermostat that
you set by the temp that you want in the cabin. The expansion valve
enable the freon (or whatever gas is in there) to 'expand' thus cooling
itself in the process. This 'cooling' works to pick up heat in the cooling-
coil and 'exchanges' the heat vide the medium of the gas to the outside
air.
so , the cooler you want it , the smaller the aperture , the more
pressure in the high pressure circuit , the harder the compressor
works and more load.
the warmer you want it , the bigger the aperture , the less pressure
on the high pressure circuit , the less load on the compressor.