A few warmer days here, so had the air con on for the first time in a while - it smelt really stale and musty. Did a search on t'internet and top tip was to spray aerosol disinfectant into the air intake with A/C on full (not on recirculation).

You can buy special stuff for this, but I found that it worked very well using Dettol anti-bacterial spray (kills 99.9percent of all germs DEAD). Lysol is the popular American equivalent brand. There are loads of these available in the supermarket and not expensive.

Run vehicle with aircon on cold and blower fan on high, vents all open, set to blow to feet and face, and the car windows open. With blower on full, outside the car feel around the black plastic grille between the windshield and the bonnet/hood with your bare hand - you should be able to feel the air flow going in at two areas, one on each side of the car. Spray directly into each of these areas for 10 seconds, then repeat after a few minutes - if you go inside the car you will be able to smell the disinfectant coming out the dash vents. Switch the aircon from cold to hot and repeat.

This will ensure that some disinfectant is on the evaporator coil, and on the ducting, including the warm ducting. The smell is pleasant enough, but the germ killing is what will avoid mustiness.

Now for the rear aircon, switch to rear control, set to cool and max fan on the overhead controller. AHA! the air intake for the aircon ducting to the rear overhead vents is from the trunk area - on the right hand (driver's) side in the UK. So open the trunk/tailgate, and on your right you will hear the fan sucking air into two slotted grilles. Spray some disinfectant into there as well - you'll note the same pleasing smell coming from the overhead rear vents.

JOB DONE. Very satisfying, and provided you have wiped up the yoghurt spilt three weeks ago under the child seat, your van will smell fresher and be a more healthy place with the AC on. Not a bad job for less than £5 and less than an hour's work. You might have to repeat this a couple times a year, depending where you live.

Happy Motoring.