General: C70/Volvo Heater Blowers

[FredGraham]

Cheers for that, truth be told I don't know whether I'm learning more & getting more confused at the same time. I expect it will all become clear eventually.

[zapcity1]

Hi Fred,

I remember reading this thread a year or so ago on the US XC forum. Identical to what I experience with my XC70.

http://www.volvoxc.com/forums/showth...in+temperature

I'm glad it's not only me who finds the way the system works uncomfortable. I wonder if the CCM firmware around this time was different?

[Baxlin]

Originally Posted by FredGraham

Thanks Clan, just checking something not mentioned. I'm normally at 21 degrees, but not with the AC on, can't remember last time I used AC.

The danger of not using AC is that when you want to use it you won’t be able to, as it won’t work.

As Clan said, best leave it on Auto and let it do its job. (OK, with a C70, possibly switch it off when the top's down, but TBH, as top down messes up the MPG anyway, I just keep mine on Auto.)

I’m relieved to have dual zone AC, as Mrs B likes a different temp setting!

[Welton]

Originally Posted by Clan

if the outside is cooler than 21 c the AC won't come on , if the outside is over 21C ( Like last summer ! ) It will come on to reduce the temp to 21 C . Also the AC Comes on when the system is defrosting , so best leave AC switch on all the time … AUTO does that for you anyway ..

I have the Volvo technical manual for the climate control, once the a/c is requested (basically the 'Auto' function) then as long as the outside air temperature is above -5 deg C the compressor will function continuously under the control of just 2 sensors; the Pressostat on the low pressure side (looks for no less than 1.65 - 1.90 bar) and the Evaporator Temperature Sensor (looks to maintain the evaporator at +1 to +3 deg C).

The compressor has a fixed displacement and basically maintains the air conditioning cycle permanently, some will report that they can hear the compressor cycling on/off but sometimes more frequently than others - this is purely the physical state of the refrigeration process; it's under more strain in hot weather than it is in cooler weather so takes a variable amount of time to maintain system pressure, this is normal.

With the a/c constantly on the climate control will use heat to maintain the cabin temp in winter and the occupants may benefit from increased demisting function, personally I leave the a/c off as I don't like feeling the compressor kicking in although it actually runs for 10 seconds upon each engine start regardless of whether it has been requested or not to help keep the compressor lubricated.

Basically once the a/c is requested it stays active constantly summer/winter regardless of outside air or cabin temps.

The climate control should, in Winter, (when the outside temp is lower than the cabin) direct airflow to the feet and the windscreen only. In summer when the cabin temp is close to or higher than outside then the airflow is directed to the face vents for effective cooling of the cabin and occupants. Once the cabin is at the 'requested' temp then the airflow will reduce significantly and the airflow temperature will regulate to keep the cabin comfortable, this may mean that in winter the airflow temp begins to feel cooler but this is ok and prevents overheating the cabin; similarly in summer the air flow temp can begin to warm slightly but as long as the space is comfortable it is working correctly. If the fan speed is always too high then there's a fault with one of the sensors somewhere.