Curing air conditioning smells

Posted on July 2nd, 2014 by Rob Marshall

mouldyAs June has bestowed fine weather across much of the UK, reported air conditioning faults have rocketed. If a stench, similar to that of a teenage boy’s socks, is fired through your dashboard vents, during the first thirty seconds of switching on the fan, consider taking action.

The problem is caused by bacteria build-up on a large ‘cold radiator’, called the evaporator, which is buried deep inside the heater-box, behind the fascia. Air, blown over the evaporator, becomes chilled but it also sheds moisture, most of which drips through the heater box and into a tube that leads outside. This is why, after stopping on a hot day, when the air conditioning has been used for at least 30 minutes, a harmless pool of water collects beneath the car.

Unfortunately, some moisture remains on the evaporator and the resulting damp is an ideal condition, in which microorganisms thrive. The horrible smell is caused by bacteria (plus its associated waste products and spores) being fired through the vents and into the car’s interior by the fan. Unsurprisingly, it is not healthy for occupants to be exposed to the brief, but intense, microbial ‘blast’.

Last week, I discovered a mild case of bacteria build-up on the evaporator (pictured), taken from a Peugeot 407’s heater-box that I stripped down. Scrubbing bleach into the part, then rinsing it thoroughly, killed the unwanted germs.

Understandably, most motorists do not wish to remove their car’s dashboard and strip down the heater-box, just to clean it. Although some garages and air conditioning specialists will advertise a cleansing service, there is no dismantling involved, meaning that you can do the job at home instead, without either getting dirty or even opening the bonnet.

Air conditioning cleaner aerosols, therefore, are far from gimmicks. Priced at between five and ten Pounds, they are applied inside the car and their vapours kill the microbes that inhabit the heater-box, including the evaporator. Most types are perfumed, which leave a pleasant fragrance behind. Therefore, as part of your pre-holiday checks of the engine coolant, oil, et al, consider treating the ventilation to a clean – you and your passengers will certainly be healthier for it.