For my first few months of ownership ('06 R53, automatic temperature controls inside the car), the air conditioning system has seemed to work adequately. However...

I recently found that I had the dreaded "bad resistor" issue with my low speed fan circuit and have replaced the radiator fan, which now works as it should (A/C on = low speed fan on). But I can tell the cool air isn't always coming through the vents as it should. I bought and installed a R-134a refill kit (with gauge), and my A/C system took the pound of refrigerant.

Still, it's not right.

As of now, it's hit and miss. The system does compress and I do get cold air out of the vents sometimes. But other times, when I think I should be getting cold air, I can tell it isn't blowing cold as it should. Is there a way to test the clutch? Can I spin the center of the clutch by hand (turning the compressor) to see if there's any binding? (I could do this on older cars.) And if I can turn the compressor, does that mean it's okay? If the clutch is burnt, is there a visual sign?

Before I go off the deep end worrying about compressor or clutch replacement, I'd like to know more about how/when/why the compressor kicks on. Is it a computer controlled thing? And if so, when? Is there a relay that might/could work intermittently? If the system is overfilled (not ruling that out), would that make the compressor NOT compress under any circumstances? Could I have blown some seals with my recharging service?

"Search" turns up tons of unrelated information, so apologies for starting a new thread.

 

Follow-up... (lots of people read the above post, but no responses)

After driving around today in mild Texas 100* heat, the A/C was still cycling on and off - then wouldn't charge at all. Side note: because my power locks were also cycling up when I slowed to around 10mph (not supposed to do that) I though my battery was weak or my general module was burning up. Batt tested fine @ AutoZone.

I came home and put the hose/gauge (came with the refill kit) back on the A/C valve. I tried watching the A/C clutch and heard it trying to engage, but it didn't stay engaged. As the clutch would engage, the pressure on the gauge was rising quickly well into the red zone, then dropped back to the edge of green when the clutch let go, only to rise again, etc.

I decided to just let some pressure out of the system - and that was the answer! Whatever system pressure monitor the car has was shutting down the A/C clutch under that much pressure (to save the system, I'm sure). Pressure now stays in the green zone on the gauge and the cool air stays on.

 

So are we to conclude from this that you put too much refrigerant into the system?

 

Absolutely. I didn't think the system could take "too much", but I guess the pressure in the refrigerant can is more than the pressure in the system. And though the kit came with the gauge and hose, it wasn't reading consistently so I couldn't tell what the actual pressure was.

 

One last follow-up note...

My MPGs are back up into the high 20s (from 23-24) just from fixing this problem. I suppose the constant on-and-off of the A/C compressor wasn't giving the engine the chance to even out and run smoothly. Such a big difference from such a small correction.

 

I had the same issue with my '06 R50. She was blowing but wasn't cooling (I live in SE Texas where it's hot and humid 11.5 months a year). I took it into a trusted shop and they put it on the gauges. They were bouncing everywhere. They tried several different procedures but finally concluded the pins in the compressor were gone. Why? Not enough refrigerant in the system. The specs are .91 pounds - too much or too little it blows (no pun intended). The remedy? $2500 - new compressor, evaporator coil, expansion valve, and water pump (this was beginning to leak and since it was already apart no reason not to replace it). Now it cools, but when it's really hot, 98 degrees +, it takes forever to cool and then only on recycled. All that to say, monitor your compressor with the over-/undercharging. Glad things worked out for you.