Cooling Fan running high all the time

[veektor]

There is a Russian saying about people like me, goes along the lines of "Live and learn, and you'll still be an idiot when you die." I was desperately trying to get Astrid ready for the upcoming trip, and went with what I've done in the past, instead of spending extra time on research. I had no idea there were different methods to control the A/C. At least I now understand why Volvo made the LOW A/C valve so difficult to access:to keep idiots like me from jacking around.

I'm going to call around to see what it will cost to have a shop evac and fill the system, but let me do the part replacements on my own. I hate the idea of releasing more of the refrigerant into the atmosphere than what already escaped through the leaks. I also don't trust my ability to accurately fill the system by weight.

[veektor]

The system on your S60 uses a physical thermometer probe and cycles compressor due to evaporator temp. If you put fan on high speed and the car is hot, 95F inside then it might be as high as 40 psi and may not cycle for a bit but one the air from vents gets into the 40's the compressor will start cycling as the evaporator temp is getting to freeze point and needs to shut off compressor for break for thawing. but otherwise that is too high pressure for that car for low side. You overcharged it.
The cycling pattern of orifice refrigerant control systems using a pressure switch is different than for expansion valve with thermal evap air probe. Rpid cycling on pressure switch systems occurs when low but with thermal probe systems it occurs when it is cooling fine especially with lower fan speed.

Jimmy, you were spot on! I hooked up the pressure gauge and it read 70psi. I said a Hail Mary and a couple of Hail BillNyes, asking forgiveness for releasing excess refrigerant into the atmosphere. Once the pressure went down to around 40, the compressor would kick on and stay running without cycling.

I was an idiot to mess with the A/C in the first place. I had endured the punishment of driving in great discomfort through the high plains of Colorado and all of Kansas on a 90F day. Glad it wasn't closer to 100F. Sucks to know it was unnecessary suffering and a self inflicted injury.

[THolland]

Hi. my son's 2005 XC90 2.5 AWD cooling fan just started acting up, seems like similar symptoms to what I am reading in this thread? It is January here in MA and quite cold, so AC operation is not clear or needed aside from when defroster is running. The issue with his car is all of a sudden the cooling fan RPM gets very high, very loud and stays at high RPM. coolant temp is normal, not hot at all and sometimes this happens at startup with engine cold. The RPM will vary though, drops low after a period of time but then races back up to high? Any thoughts on debug of this issue?

Thanks. - Tim

[abscate]

The engine coolant temperature sensor (ECT) could be out of spec - if you are handy with a VOM you can check resistance to spec. Ill link to that data shortly. Its a fairly expensive part to replace on a guess, though.

Found it in my 'Catherine' maintenance thread

viewtopic.php?p=550139#p550139

[THolland]

Is that the sensor that is mounted to the thermostat housing? If so, that whole assembly is new (within the last year). Tstat and sensor sold as as a single unit now, replaced mine as the Tstat was stuck open.

[abscate]

excellent. You will be well practiced at doing that job again.

Test the resistances to see if it is good