I have a 1997 plate X300 XJ6 4.0. I started recently to get a damp smell from the air vents when I turn on either the heating or cold air. When I use the air con it seems to go away when turned up high. Any advice or help on this issue would be really appreciated ?.

 

Sounds like mold in the system.
Buy a bottle of lysol antiseptic spray. Start your car, turn on the A/C system full blast, and make sure it's set to pull air from the outside (the recirculate button should be off). Finally, roll down all the windows. Then, start spraying the lysol into the exterior air vents between your hood and your windshield.

 

Here is how we did it at the dealer back in the day.
All these TSBs are somewhere on this forum. I uploaded HUNDREDS.

bob

 

That's a pretty cool procedure I had not seen before. I wonder if we could substitute something like Febreeze or Lysol aerosol cans connected to tubes?
I have an air compressor and could probably create a tool setup like that, but not sure what the AC duct cleaning solution would be.
Hmmm.... my wife has a selection of essential oils ...
Ooh wait -- how about that air freshener that's supposed to be like a "new car" smell....

 

The Lysol will work fine but be prepared to have the car smell like Emergency Ward 10 for about a month.

Larry