Automotive AC Repairing and Replacing – Cleaning the Evaporator Core

Some vehicle manufacturers have had problems with an unpleasant odor originating in the AC system. This unwanted smell can originate from bacteria on the evaporator core. The environment of the evaporator core includes darkness, temperature changes, and lots of moisture, which promotes bacteria to grow on the surface of the component. This causes the odor to be sent out to the vents when the blower is turned on. The two ways to repair this problem include replacing the evaporator core or treating it with a chemical. There are several companies that make the chemical product. There are a couple of ways that this substance can be used on an AC system.

Apply Chemical onto the Evaporator Core

Adding the chemical directly onto the evaporator core surface is a very effective method of treating the bacteria problem. This method of treating the evaporator core will often not be possible due to the lack of an access point to get a clear shot near the evaporator core. The steps are listed below.

Spraying Cleaner Directly into the Evaporator Core

1. Gain access to the blower motor, blower resistor, or evaporator temperature sensor. This can usually be done by removing the glove box or by removing the trim panel on the passenger-side footwell area.
2. Remove the component that is the easiest to access and store the fasteners in a safe place.
3. Shine a light in the opening that was created by the part removal. The evaporator core should be visible from this location.

An evaporator odor eliminator substance is available to help eliminate the odor that occurs when bacteria is allowed to exist on the evaporator core. This substance can be directly applied to the evaporator core if possible or it can be directed into the duct box drain tube and sprayed up into the opening. The user should closely follow the directions that the chemical manufacturer provides to get the best

4. Install the nozzle hose onto the spray can and direct it inside the duct box.
5. Spray the whole surface of the evaporator core with the chemical.
6. Reinstall the component that was removed.
7. Wait several minutes for the chemical to attack the unwanted bacteria
8. Roll the windows down. Start the vehicle and turn the blower to the highest setting for several minutes.

Using Cleaner Indirectly at the Drain Tube

Add Chemical through the Duct Box Drain Tube

1. Insert the nozzle of the chemical cleaner into the duct box drain tube.
2. Depress the nozzle valve to fully add all of the chemical into the duct box.
3. Roll the windows down on the vehicle.
4. Wait several minutes and then start the vehicle and run the AC for several minutes.

The process of adding the chemical to the AC system is a fairly effective method of killing the bacteria on the evaporator core. A few manufacturers have designed their AC systems to run the blower motor for several seconds after the vehicle has been shut off in order to dry off the evaporator core, which reduces the chances of having this problem occur.

Another method that any operator can follow is to run the AC system in the fresh air mode as much as possible. The action of pulling in fresh air from outside the cab assists in keeping the bacteria from growing on the evaporator core’s surface.

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