Air conditioning compressor failure?

[robertd]

My '99 2.5L 5-speed Boxster was bought used 18 months ago with an unknown service history. I bought it anticipating having to do a lot of DIY repairs. Fortunately it has been mostly trouble free . . . up to last week. I have had some idling and rough running problems for a while. I had already determined through research here that my MAF sensor was probably on it's way out. Last week it started stalling and running really rough and finally kicked a CEL for error codes 1123 & 1125. A quick search here suggested that I ignore the O2 sensors for which these codes relate and test the MAF sensor. Anyway, after testing and replacing the MAF sensor and removing and cleaning the throttle body and idle control valve all seemed to be well. The car was running great with no surging, stalling or wavering at idle.

Today I had a lunch appointment that required more formal dress than my usual jeans and T-shirt. I jumped in the Boxster and with the late May sun bearing down on my head on this 80° spring day, decided to leave the top up and run the A/C. I drove about 5 minutes before realizing that the air coming through the vents was still blowing hot. Previously the A/C has worked flawlessly. I checked to be sure the A/C was on (it was- I usually just hit the AUTO button) and that the temperature was set appropriately (70°). I cycled the snowflake button a few times and that is when it happened. I felt the compressor kick on and then the car started to buck as I was slowing for a stop at around 30MPH. I put in the clutch and the car nearly stalled, recovered and then emitted a loud metallic squealing sound from right behind my head. At that point an acrid burning smell permeated the cockpit. I turned off the A/C, lowered the windows and continued on to my lunch appointment a bit sweaty and perturbed.

Upon return home from lunch I first changed clothes then pulled the engine covers and enlisted my wife for assistance. With me standing over the engine bay with a flashlight I had her start the car then press the AUTO button on the A/C control panel (thus activating the A/C). Everything ran normally but she reported warm air from the vents. We let it run for 2-3 minutes like that with no change. I then instructed her to cycle the snowflake button. When she did I heard the compressor kick on and saw both halves of the pulley start to rotate. It ran for maybe 15 seconds and I was starting to smell the rubber/electrical burning smell again when the compressor pulley just stopped turning! The belt slipping over the pully made the same screeching/grinding sound from earlier and smoke started pouring off the pulley that matched the acrid smell from before. My wife, who's head was mere inches from all of this in the driver's seat, started to vault herself from the car as if it was about to blow. I managed to convince her to turn the key off before she bailed out ;-)

So, here is my question: is this simply a failed A/C compressor or should I be looking for something else that may have caused this to occur? In researching this this afternoon I have determined that my A/C system has likely been running low on refrigerant (lots of periodic pressurized air hissing noises moving back and forth along the passenger side when the A/C was running). Are there any other parts that typically need replacing at the same time as the compressor? I have a Bentley manual and am pretty handy but A/C systems are something that I have basically no experience with.

Any advice, insight, etc. from the Guru's would be appreciated.

Thanks and sorry for the long-winded-ness.

[RFM]

Looks like a blocked compressor, a trip to dealer or AC specialist is a must to replace the compressor, examination why he is blocked, cleaning the AC system, changing the dryer, inspect where the leak is and repair, replace the poly V belt and filling up the system.

[Glyn]

Before changing the compressor i would check the condition of the polyrib belt, this may just be worn and a little loose through stretching.

When you engage the compressor there is quite a resistance to turning, a loose belt will cause the slip and of course the friction will induce heat - hence the burning smell.

Clearly you will need to change the belt anyway so i would do this first, correctly tension the belt and try it again.

Secondly if you know you were low on refrigerant - which also contains a lubricant for the compressor it could be that you are completely drained of refrigerant and that the compressor through heat is trying to sieze up, however when low on pressure in the air con system the compressor should not engage as it has a pressure sensor- however this sensor could be faulty and allowing the compressor to drive without gas/lubricant.

Get the system regassed then change the belt and try it out again, You could be right about the compressor being knackered and of course if you regass then you will need to pay again for another regass when the compressor is changed, but it is unusuall for a compressor to fail and the cost of a compressor is high

[robertd]

I considered the polyrib belt. Problem is I can't move my passenger seat to gain access to the front engine cover. See my other post here. I may try getting a recharge to see what happens. Thanks for the advice.

[Glyn]

Right, read your other post. Does your seat not have the quick release lift ups either side of the back rest? Both my Boxsters had these though i have not had the full electric seats so i guess there could be a difference, Lift them up and the seat tilts forward - enough to remove the inspection panel and to get at the securing bolts that hold the seat in place

[robertd]

Right, read your other post. Does your seat not have the quick release lift ups either side of the back rest? Both my Boxsters had these though i have not had the full electric seats so i guess there could be a difference, Lift them up and the seat tilts forward - enough to remove the inspection panel and to get at the securing bolts that hold the seat in place

Glyn- Passenger seat has the tilt quick release levers on both sides. Try as I might they will not release the seat back. Seems the cable(s) is disconnected/broken. Driver's seat works fine.

[Glyn]

They wont be disconnected just that you have the seat powered back into the bulkhead with some force - the catches will not be releasing unless you can ease the force, suggest getting another person to apply force to the seat back at the midway point and whilst force is being applied then pull the lever - this should assist the catches to release

[robertd]

They wont be disconnected just that you have the seat powered back into the bulkhead with some force - the catches will not be releasing unless you can ease the force, suggest getting another person to apply force to the seat back at the midway point and whilst force is being applied then pull the lever - this should assist the catches to release

See other post for seat update. Glyn, you were right about the tension of the catches being the problem. Thanks! :cheers:

Edited May 26, 2008 by robertd

[robertd]

Now that I've managed to get the passenger seat out of the way I opened up the front engine cover for the first time:

The polyrib belt is definitely in need of replacement. Looks like it's about ready to go at any time :eek:

Also, the A/C compressor pulley/clutch seems to be oozing grease:

Any chance I just need a new compressor pulley/clutch assembly? Any chance they sell Porsche A/C pulley/clutch assemblies?

[RFM]

As mentioned in my earlier post, ( let ) find out why the clutch is damaged.

[brunel]

I had the same problem, expect my compressor has seized solid and that has sheared the rubber centre. Any ideas how the powersterring res comes off, the manual is pretty unhelpful and you have to take it off to access the a/c hoses.