As cars age, problems with foreign and unpleasant odours can become a problem. Most often the more offensive odours are the result or liquids being spilt or otherwise entering the automobile where these are allowed to remain until mould and mildew forms, creating an unpleasant scent. While water spills or rain entering through open windows are obvious mildew may also form and create problems in a less conspicuous place and that is in the automobile's air ventilation system. This water accumulation is most often the result of condensation which occurs when cool, air conditioned air passes through the ventilation system on hot, humid days.
Start the car engine and with the windows closed. Set the car ventilation system on "vent' with the air circulation from inside the car. Set fan speed on high.
If there is mildew accumulation in the internal ventilation duct system you will immediately sense a strong, unpleasant, vinegar-like odour.
If there is no odour, switch circulation from inside the car to outside, leaving the fan on the high setting. Check for vinegar-like odour. If there is no odour the problem is not in the ventilation system.
If either of the above steps results in a strong acetic smell resembling vinegar there is a problem with mildew or mould in the ventilation system. Proceed to section 2.
Locate the fresh air intake portals on your car. These are most often found at the bottom of the windscreen and just above the bonnet.
Start the engine and the set air ventilation system on high fan speed. Set circulation control to draw air from the outside. This outside air setting is very important.
With the engine running and the above settings on the air ventilation system selected, generously spray Lysol disinfectant into the fresh air intake portals on both sides of the windscreen. Pump the spray 10 to 12 times on each side.
Inside the car you will smell the scent of the disinfectant working its way through the system and neutralising the mildew.
Inside of the automobile, place the shop vacuum nozzle against the air vents on both sides and in the middle of the car dashboard panel. Use the vacuum to assist in drawing disinfectant through the entire system.
Repeat step five on all inside vents.
Allow system to run and circulate disinfectant for 10 to 12 minutes. If acetic odour persists repeat the process by spraying additional disinfectant.
After 10 to 12 minutes cut off the air ventilation system and stop the engine. From inside the car, spray disinfectant into each inside the air vent. Wipe the excess with clean rag.
For heavier accumulations of mildew or mould, you may have to repeat disinfectant application until odour is neutralised. In hot, humid areas of the country this process may be required periodically as mildew may return as new condensation occurs.