[whitelion65]

Check that the tube to drain condensation from the evaporator isn't blocked. Even without blockage, you end up with organic sludge building up from microbial growth. I treated mine buy setting the system to full fan, air-con off, recirculate, and emptied half a can of Glen-20 up under the dash. This has helped.
Try to turn the air-con off a few minutes prior to reaching your destination to allow condensate to dissipate.
If Fraud do an air-con clean for you, they will do much the same as above, using a fancy branded product, and charge you a few hundred dollars!