Bad smell

Pretty sure there is no Cabin Air filter on that, but will update if I find anything.

Does it smell moldy? try to describe the smell.

Is your antifreeze full?

The smell reminds you of something that got into the system somehow and died. A rotten smell. However I'm not sure how that could happen. There's no access. It's been there for about a year. I've gone so far as to have my air condition system vaccum out. The only thing I haven't done yet is drain the coolant. There's no leaks anywhere. The cooling system has a good color. The engine has 60,000 miles on it. I'm at a total loss. It's a great runner. Any suggestions would be welcome. Thanks

The reason I asked about the coolant is a possible heater core leak...but you ruled that out. There is a mold build up that can accumulate on the evaporator core. Sometimes you have to be create to access it. Often pulling the blower motor will allow access. One chemical can be sprayed on it and rinsed , another chemical is used to deodorize and disinfect the sytem at various points including the vents, a third is added to the washer bottle.
Various companies make products similiar, I use a castle chemical product that comes in a kit.

Thanks for the new info. I'm gonna try whatever I can to rid myself of this smell. Thanks in advance for any ideas you might come up with.