Does anyone know if the compressor works at different levels based on outside temp and commanded temp inside?<P>In simple terms, does the compressor either come on or off, and no in between levels of use? <P>I ask this because I wonder if keeping the a/c on at all times is a good thing, even when the outside temp is cold and you are commanding warm temps from the selector knobs?<P>Sam<BR>
A/C Compressor in automatic climate control
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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by V70SAM:<BR><B>Does anyone know if the compressor works at different levels based on outside temp and commanded temp inside?<P>In simple terms, does the compressor either come on or off, and no in between levels of use? <P>I ask this because I wonder if keeping the a/c on at all times is a good thing, even when the outside temp is cold and you are commanding warm temps from the selector knobs?<P>Sam</B><HR></BLOCKQUOTE><P>Depends on the outside temps. But yes, typically the a/c runs and the air-blend door mixes warm air from the heater core with the cool a/c air to get the interior temp just right. a/c will be shut off when the outside air inlet temp is cool enough to buck the heat from the heater core.<P>Also, when outside temps are above freezing and if the windshield defroster is turned on, the A/C will kick in to dehumidify the air blown onto the windshield. (My T-bird auto climate control did this, I noticed the S60's did, too) Of course, cold air doesn't feel good or help to de-fog the window, so warm air is added from the heater core to raise the temps. <P>The trouble is, the instant you turn off the a/c the water that was condensed on the a/c evaporator core will now turn into gas and then condense on the window and block your view!! So you have to leave the system on defrost and leave the a/c on to keep the water in the evaporator core. It's a pain, I don't like wasting the gasoline to run the a/c when it's 40 degrees outside.
So from what I can gather from your reply. The compressor works only at one level - On. It's to variable and as such dependant on the load you are demanding from it. (say to cool your car to 65 degrees on a 100 degree day vs just keeping the temp at 70 degrees on a 75 degree day)<P>Sam<BR>
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by V70SAM:<BR><B>So from what I can gather from your reply. The compressor works only at one level - On. It's to variable and as such dependant on the load you are demanding from it. (say to cool your car to 65 degrees on a 100 degree day vs just keeping the temp at 70 degrees on a 75 degree day)<P>Sam</B><HR></BLOCKQUOTE><P>Yes the compressor can only be turned on & off with the clutch. Note that the compressor can be <I>cycled</I> by turning it on and off if it doesn't have to stay on, say at low cabin temperatures. But yes, the compressor is a binary device, on or off.<BR>
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by V70SAM:<BR><B>Does anyone know if the compressor works at different levels based on outside temp and commanded temp inside?<P>In simple terms, does the compressor either come on or off, and no in between levels of use? <P>I ask this because I wonder if keeping the a/c on at all times is a good thing, even when the outside temp is cold and you are commanding warm temps from the selector knobs?<P>Sam</B><HR></BLOCKQUOTE><P>hi Sam!<P> AC compressors typically cycle on and off; they can't stay on all the time or there's a risk of actually causing a freeze-up in the condenser. (temp sensors were used in some vehicles to keep the compressor from engaging when condenser temps are too low,... i haven't checked this in the Volvos.)<BR> the Climate Control 'brain' mixes warm air with the AC'd air as necessary to keep it at the desired interior temp.<P> one 'disadvantage' to having the AC engaged for some more sensitive individuals is that it dehumidifies the air. (this is why the AC compressor is engaged with the Defroster.)<BR> another is that (as someone else mentioned) it causes a build-up of condensation inside the system when the system returns to ambient temps. (think about the condensation that builds up on the outside of a cold drink when the outside temp is higher; same principle.) if the system isn't warmed up to dry out the mosture that will form before the vehicle is shut down, there can be enough moisture collecting in there for ugly stuff to start growing, causing (at the least) a musty smell, or worse, molds and such. this can be easily avoided by making it part of your pre-shutdown routine to disengage the AC a few minutes before shut-down to allow the system temps to return to ambient while there is enough airflow to dissipate the condensation that inevitably forms in there.<P> just some more things to consider; i hope that helps answer your question!<P><BR>cheers!<BR>e<BR><P>
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