When i turn on the ac or just after i turn it off, a very bad smell gets out of the vents. Any advice? Last year i went for air con maintenance (replaced the fluid, cleared the area near the pollen filter and sprayed antibacterial spray around the pollen filter input). But the smell is not gone, just getting worse and worse. What needs to be done? Any advice? If turn on the air con at max fan speed and spray antibacterial at the pollen filter vent, will it be enough to do the trick?