Greetings! I have a 2004 R53, purchased new in March of '04. ~290k miles. It has the MANUAL A/C controls.

Last summer, and again now that the temps are warmer, I've felt like my A/C isn't operating up to snuff. I just checked it and right now, the ambient temp is 85ºF, and center outlet temp is about 70ºF, blower on '4', temp set full cold, recirc on. Low side pressure is about 40 psi, and high side is cycling 225-250 psi. So, roughly within specs as I understand them but a bit high.

My question therefore is: What is the expected behaviour of the radiator fan? Just now with the A/C off, the fan was off. When the A/C was first turned on, it came on at a low speed -- I could barely hear it and had to look to confirm it was running. After a bit it would spool up for a few seconds, then spin down again to that slow speed. When it was running noisily the high side pressure dropped to ~225 and rose again to about 250 when the fan spun down. My gut is telling me insufficient airflow over the condenser but I don't know exactly what to expect of the fan.

Thoughts?

Thanks!

 

Sounds like your fan is operating as designed. The low-speed fan should come on when you turn on the A/C or when your temp hits 214F. The hi-speed fan comes on at 234F. Have you checked to ensure that your compressor clutch is engaging? It sounds as though you might be having a Freon issue even though your pressure readings don't seem off. There is a low-pressure switch attached to the A/C line that runs from the evaporator to the condenser. Low Freon will prevent your A/C clutch from engaging and prevent cooling.