2008 Lexus gs350 AWD. The other night I hopped back into the car after I picked up some food and when I was driving home the car made a screeching noise from the engine and the rpms started bouncing around. Then the dash said check a/c, and I just turned off the ac and the noise stopped. When I parked, turned it back on and the same noise, smell, and bouncing rpm started. I isolated the sound to the serp belt. Today I was able to take a look at it and the serp belt looked pretty bad, so I started by replacing that. Once I got the belt off I was able to spin the compressor and tensioner easily, no roughness, and when driving turning the ac on and off I could not replicate the issue. I just went out to run an errand, and it was colder (45 degrees) so I tested it again and the rpms started jumping around again but no smell or crazy noise this time, but the engine stalled when I turned the ac off again while parked but when driving it did not stall after turning on and off. I'm thinking it is something to do with the compressor, but not 100% sure. Any help is appreciated. I will try to post a video of the rpm's

 

rpm video

 

Sounds like your compressor seized to me. When the compressor failed in our rx330, it sheared the shaft internally, so the pulley would still spin, but the AC wouldn’t work. Flashing light and check AC message.

 

Sounds like the ac compressor imploded. If thats the case then its a pretty costly repair. When an ac compressor breaks implodes it shoots off debri all through your ac system. Simply slapping an ac compressor and calling it fixed will not fix it. Sure it may work for a month or two or maybe even more but more likely the compressor will blow out again.

I had this happen on my GS, this is what I did and the parts I used. You will need an ac compressor, I went with denso reman, I would avoid cheap aftermarkets as they do not last. Then you will need a new condensor, I used a cheap china brand, make sure it has a new filter inside of it. Super difficult to clean out a condensor, as the ports are so tiny inside. Then I purchased some freon line flush, the mechanic fully flushed the evaptorator, and all the lines making sure no blockages. Replaced the schrader valve for the high and low side. I think I also replaced the expansion valve aswell

Then vacuumed the system, and filled it by measuring the weight of the freon going in.

 

I think the expansion valve is a dashboard out situation so you'd definitely remember that.