Hello everybody, it's been a while I have a couple of questions regarding my 1999 SL 500
Do the expansion valve possibly leak?
My AC stop cooling out of the blue.
My Indie tells me that he tried to charge the system but my expansion valve is stuck and needs to be replace for $450.00
OUCH, he also tells me that that smell coming from the vents is Freon gas leaking into the cabin possibly the evaporator, 20 hrs labor $ 3000.00 plus the first $450.00 he explains to me that he will change the valve first since he knows for certain that it is indeed gone but not to get my hopes up because the odds are against the evaporator. Does this sounds reasonable to you guys
thanks.

His diagnosis is indeed plausible. For shop work, his prices are somewhat reasonable.

Freon is odorless, non-flammable, and is not corrosive. The smell is most likely a heater/fitting leak and you are smelling the anti-freeze. I would have him or someone knowledgeable add fluorescent dye and top off the system with freon. Then run for a week and bring it back in and lift the vehicle and use a UV light to verify the presence of dye or lack thereof.

R134 is pretty much odorless, but the oil used with it is not. If a leak is bad enough you can indeed smell it.

Agree, but since we have no idea what the odor smells like, we cannot know exactly what it is. There is no way I would trust anyone (unless I had history with them) to make these types of repairs without a through evaluation of the issue. But that's only my opinion. Do what you wish, it's your money....

If the evaporator is replaced, the expansion valve can be replace with no additional labor.
I would attempt to pinpoint the leaking component before having repairs made.

New expansion valve and new evaporator and dryer, also since we were there, new heater core.You can can do this if you have the patience and a delicate touch, this is a time consuming and delicate operation, that requires diagrams and prints, is easy to damage trim, clips and fasteners and plastic parts if you don't know what you are doing, 2 weeks and two days for me and even though I learn how to do it I don't think I'll do it again.
Thanks for the responses