We own our 4th Volvo now. 2 out of the four have had horrible smells emitted from the A/C. One was a "cat pee" smell after it rained. But this time, I am getting a "dead animal" smell that I can't get rid of! Have had A/C checked, filter changed, and thoroughly looked at under the hood, etc. Please, any suggestions??

 

Could possibly be a dead rodent.

In past I have used Tilex to help get rid of odors.
I would remove the air filter and try spraying Tilex through the air inlet under the hood while the fan is turned on high. If you leave the filter in place, the tilex will get trapped by the filter.

Tilex has bleach which will help kill any mold in the system. Might also nuetralize the rodent smell.

 

It is probably a condition called "dirty sock syndrome"I am in the a/c buisness as a tech advisor and we come across this from time-to-time in home units. It is a biological agent that attaches to the aluminum fins of the evaporator coil under the dash and gives off that bad smell. About the only thing that I know of that won't harm you and get rid of the smell is to get an ozone generator and put it in the cabin and point the discharge of the generator at the a/c intake under the passenger side dash and let it run overnight. I've done it before wiith great success. Just un plug it the next morning and open the car door and let it air out. Unfortunately with time the smell might come back. The only way to permenantly stop it if that's what it is , is to have the a/c coil coated with a special coating designed for that purpose, either black epoxy or Bronze-glow coating. (expensive fix!) Hopefully the ozone will do the trick.

 

When was the last time the cabin filter was replaced?