How to clean an air conditioner evaporator

According to the magazine “Motor Train”, the interior of your car can contain up to 10 times more pollutants than air in an equivalent space outside the car. Manufacturers have been struggling to solve that in recent years with improvements in filters and air ducts in the cabins. A common source of problems is the air conditioning system.

The A / C evaporator gets wet by passing moist air over its cool surface. This humid environment is a good place to form mildew and mildew and to gather dust and pollen, finding its way back to the air system. Bacteria grow exceptionally well in this area, which becomes warm but still feel damp when you turn off the car. This contamination must be cleaned regularly.


  1. Check the air conditioning system under the hood of your vehicle. You are looking for the frame of the evaporator / heater housing. It is in the firewall that separates the engine compartment from the passenger area. It will be a plastic box that protrudes outward from the firewall. The heater motor will be connected to the box. You are looking for the easiest access to the air conditioning core.
  2. Access the evaporator core. Many vehicles have a resistor block that is mounted on top or side of the heater case. You can extract it for easy access. You may also want to consider removing the fan and see if you can access the evaporator core. If none of these methods work, you can make a 3/8 inch (0.375 cm) hole between the evaporator box and the fan. This will be sealed later. You need a direct path to cover the evaporator core with cleaner.
  3. Spray the cleaner through the access point to the evaporator core. If you can see the core to cover it completely, that’s the best way. Many of these cleaners are foam-based, designed by manufacturers to attach to all surfaces inside the heater box, to clean and disinfect them. Fill the area with foam and let sit for at least half an hour. The foam will become liquid and will pass through the drain openings when you are finished with your cleaning task.
  4. Gently rinse the area with water. You can use a light spray with a garden hose. Have some helper look inside the vents while you do this as you can pour water into the car. If you do not feel comfortable with the hose, use a spray bottle that contains clean water to provide an extra rinse.
  5. Seal the heater case. Install the resistor block or fan if you have removed any. If you have made a hole, use RTV silicone tube to seal the opening. When you want to re-clean the evaporator, simply remove the dry silicone with a toothpick or a screwdriver to access the core. Use your vehicle for half an hour with high heat and fan at its strongest point to completely dry the area.

Tips & Warnings:

  • Consider installing a kit that includes an accessory installed to the box of the heater to which you connect a tube. You can then spray a foamy cleaning solution through the tube. This makes the task easier, and you can clean the system more often. Run your fan for a few minutes with the air conditioning turned off when you stop your car on hot days to help dry out the moisture that forms in the system.