Musty AC smell

Turn off the AC?

Is this one of those ac's with a built-in bilge like my 1991 Sovereign?

I had a 2003 S-Type R with the same problem. Dealer never could resolve it. They told me it was because of the humidity in the air. Duh!! I finally resolved it by trading it in on a 2005 XJR. Best move possible.

It probably means that you didn't use it over the winter and mould grew. It does. Any decent aircon specialist (and I exclude jaguar dealers) will be able to spray a biocide into the aircon intake while it's running (if you do it yourself - doors & windows open and nobody in the car - it's horrid stuff. Takes a few days for the smell of that to go, then problem gone. Use your aircon in the winter!

david