bendavis2

So I've never really paid much attention to the AC in my car since it never worked. I just decided to spray some Duracool in there to see what would happen. In the process I had the car running and was watching the compressor. The belt that runs across the AC compressor pulley would be rotating, and the pulley would be rotating (I assume doing some compressing), and then there's an audible click, and the belt keeps traveling, but the pulley just stops. This just seems a little strange that the compressor wouldn't go into neutral, and still spin freely with the belt. I'd doesn't look right to have the belt moving across the stationary pulley. I can't imagine that the belt would last very long and would burnish itself fairly quickly. After a minute or so, there's another click, and the belt and pulley start rotating in tandem again.

Does anyone have any idea if this is standard operating procedure, or if maybe my belt is too tight or loose, or something is wrong with my compressor?

diego944

the pulley is free turning and always spinning when the engine is running.. what you're seeing and hearing, is the clutch " the end cap " engaging and disengaging... that's what actually turns the compressor.

my84-944

This is normal. If your compressor never shuts off or never comes on...then you have an ac issue.

bendavis2

So, if my pulley is coming to a complete stop half the time, while the belt is still moving, then should I assume that the belt just isn't tight enough?

Zero10

Look closer, if the belt really was slipping you'd hear the squealing. There is a thin ring around the outside that the belt turns on that will always turn. The clutch locks it to the center section.

diego944

ahh. i think i see..do you mean that as you look at the front of the compressor pulley the whole thing seems to be turning.... then you hear a click and the very end stops turning???

if that's the case that's normal...
the ac clutch is actually three pieces. the pulley where the belt rides, the coil ( an electromagnet inside the pulley) and the face plate ( which is what you see on the very end of the pulley).

put 12v to the coil and it pulls the face plate into the spinning pulley which turns the compressor...


if the pulley the belt rides on ever stopped you would know it...very loud squeal followed by a thrown belt or stalled engine.

xsboost90

how many lbs of duracool did you put in? System takes about two lbs and if its too much/little itll short cycle like that. SHould stay on the whole time you have the a/c engaged.

mtccl

You are either seeing the clutch operate as others have pointed out or your compressor is seizing; which I doubt or you would have lots of noise and belt smoke, etc.

Either way STOP messing with it on a low charge and improper vacuum on the system or you're going to smoke your compressor.

josephsc

There is a switch in the AC system that disengages the compressor if the pressure is too low (to prevent it from eating itself). If the coolant level is at borderline, it can engage/disengage the compressor. Have tried recharging your AC system?

bendavis2

OK. So apparently I have figured out one more reason not to work two jobs and have to work on the car between 10pm and 2am. The bad light I had kept me from detecting the multiple parts of the AC compressor. Indeed, as mentioned above there is a smaller portion of the pulley that continues to rotate, even thought the majority of the pulley which is most visible comes to a complete stop.

I apologize for the question, but was just getting really nervous at seeing what I thought was a lot of extra friction on the belt.

I didn't pull a vacuum on the system, since it still had pressure and hadn't been opened. The system has dropped down to 15 psi on the low side without ever being recharged since 1983. It's not enough to convert to 134a, so I figured I'd just shoot in a can of DuraDry, DuraSeal, and DuraOil. This brought the system up to 35 psi @ 2200rpm, which is what the DuraCool gauges show as appropriate. It is now crispy cold, and even with the temps in the 90's today, I had to keep the AC on low to keep my nose from getting frostbite.

Thanks for all the help guys!


Ben
Portland, OR
1983 Porsche 944 n/a

Dustin Holt

Dude, I had the same thought you did and I was in the bright daylight.

my84-944

Woah. Did you say you added 134a to an r12 system. First thing this is very NOT RECOMMENDED. You may consider having your system recovered and Done the correct way. Proper vaccume to the correct microns then leak checked. BTW if you ever have it recovered, ya may mention it is mixed. Most tech will appreciate the heads up. I know
I would.