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.