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Steve, Service Manager
Category: Dodge
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Experience:  25+ Years experience as a professional working automotive technician; ASE L1 master technician
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Durango SLT: 2004 Durango 4.7 4WD, getting smell when A/C is

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2004 Durango 4.7 4WD, getting smell when A/C is running. Only A/C, not when heater is on. Mechanic checked it out, and said A/C is fine. Freon was full, air is cold etc. The water moisture/water that drains when A/C has been running for ahwile (under passenger side) has same smell. Ideas?
THe evaporator core for your air conditioning system is located in a plastic case up behind the instrument panel. When the A/C is running moisture out of the air condenses on the evaporator, which then drips to the bottom of the case and runs out onto the ground through a drain tube. Also, it is not unusual for organic debris such as pieces of leaves, pine needles, etc to accumulate in the bottom of the evaporator case where they retain moisture and keep things damp. This is a perfect environment for mold and mildew to grow, and this is the usual cause of objectionable odors from an A/C system.
You can try turning the A/C to recirculate position (max A/C); in this position air is drawn from the inside of the vehicle and recirculated through the evaporator. Spray a significant amount of Lysol or other disinfectant spray into the drivers floor area and let the car run for a while to circulate the spray through the inside of the case.
If this does not resolve the condition there are some commercial mildew eliminator kits on the market that your mechanic can use to spray the inside of the case and the evaporator core directly to kill mold and mildew.

Customer: replied 4 years ago.

When running max A/C mode, smell is still there. I have heard of pouring bleach/water mixture over intake vents (just under windshield) to drain and clean. Then do the same thing, this time with water to flush. Is this recommended?

I have never heard of that approach,, so I have no idea if it would have any effect. I would suspect it would not, since if the water follows the usual path of water from the cowl area (like rain water) it should not ever enter the heater case. if it did, there is the possibility of it getting into the blower motor and damaging it, or leaking out of the case onto the carpet causing discoloration.

Here is one of the professional cleaners to kill mildew, but you usually ahve to do a little disassembly to gain access to the evaporator surface to sprat this type of product on. Sometimes you can get to it by removing the blower motor or the blower resistor.

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Customer: replied 4 years ago.

I see. So using an evaporator cleaner such as the one you mentioned, just simply remove the blower motor, spray the cleaner up in there and let it work? Any other advice? Spray directly into vents as well?

Every different brans probably has specific directions on the can or in the kit. In general you want to spray it directly on the areas where mildew can grow, which is at least the surface of the evaporator core itself. I have never seen one that said to spray it in the vents directly; usually the vents are pretty dry and do not lead in a straight path to the evaporator core. I would follow the directions on the product.
Sometimes getting access to the core can be difficult; removing the blower may reveal a path to the core on yours, I cannot say for certain. Sometimes you need to start disassembling things to see what works best on different models. I have had a few vehicles in the past where I had to actually drill a couple of small access holes in the plastic case and then seal them with plugs afterwords.

You may want to ask your mechanic about this service; most mechanics have tried a couple of products over the years and he may have a favorite that works well for him.

Customer: replied 4 years ago.

Understand. I have been researching a few different cleaners, and most are used from the evaporator drain hose. I will give it a shot and see what happens. Thank you for all the advice and help! Extremely helpful!