Musty smell in interior
Occasionally, the air-conditioning system can cause a musty damp smell in the interior of the vehicle. This is due to particles of dirt, which are carried into the evaporator housing with the induced fresh air, sticking to the evaporator fins covered with condensation. When the airconditioning system is switched off, a moist warm environment is created in which the partially organic deposits of micro-organisms and fungi are broken down.This process produces unpleasant smells which are conveyed into the interior of the vehicle when the air-conditioning system is switched on again. The smell rapidly disappears due to the continuous change of air when the system is running. However, it recurs after every break in operation.Vehicles used in moist warm climates are more frequently affected by this type of smell. Often it also occurs in vehicles with horizontal evaporator fins. The droplets of condensation are unable to drain away completely from these fins and a constantly damp environment is produced which promotes the multiplication of micro-organisms and fungi. The interior of the evaporator housing must not be allowed to remain continuously moist if the smell is to be avoided. Therefore, the drainage lines must be cleaned regularly. In addition, it is important to ensure that as little dirt as possible enters the evaporator housing. Vehicles parked regularly under trees pick up particularly large amounts of dirt.
Action to cure smells
If smells ever occur, the interior of the evaporator housing must be treated with a chemical which has a disinfecting and deodorising action (see Figure 5.13). This chemical is distributed
throughout the evaporator housing with the aid of a special spray gun. Before using the chemical, locate the precise cause of the smell. This chemical can only be used to cure smells emanating from the evaporator housing. Other sources of smells such as damp carpets or the like must be treated differently. Before treatment with the chemical, the evaporator must be completely dry. This is achieved by operating the system with maximum heating at the highest blower speed in fresh air mode with the vents opened for about 15 minutes. The compressor must not be allowed to operate (unplug the low pressure switch or the magnetic clutch). Moisture in the air would condense on the cold evaporator again immediately. The blower motor or the blower resistor can be removed to gain access to the evaporator housing, depending on the type of vehicle. If possible, the housing must be cleaned by hand from inside. If a particularly large accumulation of dirt is found, it is imperative to check whether the screens and filters are intact. The chemical is distributed over the entire surface of the evaporator with the spray gun through the opening. The blower motor or resistor can be refitted while the chemical is allowed to work for 10 minutes. To ensure that the chemical cannot be carried away by condensation, it must be allowed to dry on the evaporator. For this, the vehicle heating must be operated for a further 15 minutes without the compressor running. Then the interior of the vehicle must be aired thoroughly. The low pressure switch or the magnetic clutch can be reconnected. On completion of the work, the vehicle interior must be aired for 30 minutes.
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