Got a 2002 LS430. I changed the serpentine belt about 1 month ago because it squeaked when I turned on the engine. This noise is gone but..

As of late, I've noticed when I have my A/C on, I hear a whining noise. When I turn off the A/C the noise is gone. Does anyone know what to do with this?

 

Most likely source is the A/C compressor, possibly bearing damage internally. Low refrigerant can cause it sometimes too since refrigerant carries the oil in the system. I'd suggest having someone reclaim what is in it to determine how much is currently in. BG makes a refrigerant oil that works miracles in some cases, maybe have someone add some to the system (need an injector since it is not in a pressurized can) and recharge to the proper refrigerant capacity. Frigi-quiet is the product name.

 

Thanks. I was thinking along the same line of your suggestion, but I'm not knowledgeable in this. Thanks for the suggestion. I'll look into.

 

I had the same or similar noise, and then I started getting a gurgling sound from the rear cooler box area. Turns out the freon was a little low, had it topped up and both noises are gone. The mechanic said he could see bubbles in the a/c hose view window behind the grill, check your and if there's bubbles its probably low on freon. I am guessing there shouldn't be bubbles visible in that little glass window. Must be a tiny leak in the system somewhere, when the noises return I'll try to locate the leak.