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Friday, 27 March 2009 17:00

Hey Toby 12 --- Some Air Conditioning Issues and Fixes

Written by Toby Chess

With summer only a few months away, I’ve been receiving a number of questions dealing with automobile air conditioning. It’s a good time to answer them. To read this article in PDF format with photos, click here .

 Hey Toby—My repair center recently repaired a vehicle that was involved in a front end collision. The vehicle was not running and towed in. After the repairs were completed, I took the car for a test drive and turned on the air conditioning system to check it out. I was blasted by a foul smell coming from the air conditioning vent. Did we do something wrong?
        —Jose from Scottsdale.

Hey Jose—I really doubt that your shop did anything wrong. If it smells like a mildew odor, it was probably present prior to the accident. What happens is the evaporator drain gets clogged and water accumulates in the evaporator.
    The evaporator has 2 functions, first it removes the heat from the inside of the vehicle and second, it acts as a dehumidifier. As the warm air travels over the fins of the evaporator, water condenses on the fins and drains to the outside of the vehicle.
    If the drain gets clogged, moisture will accumulate and it becomes a breeding ground for algae-like mold and bacterial organisms. As the microorganisms grow, they give off the foul odor. You can check to see if the drain is open, but that can be a bit of a challenge. A simple and cheap solution would be to use Lysol. Place the HVAC into recirculation mode and turn of the A/C system. Next, turn on the fan to medium and spray the Lysol under the dash behind the glove box. The fan motor will pick up the Lysol and transfer it through the system and, hopefully, kill the spores, mold, or algae.
    A word of caution, Lysol can discolor the dash, so make a test on an area that can’t be seen and look for any discoloration. There are also commercial products that work like Lysol. There are also some products that coat the fins of the cooler and prevent the spores from growing. Good luck!

Hey Toby—I was told that if an A/C system has been open for more than a few hours, you must replace the receiver/drier. Is that true?
        —Rick from Norwalk
Hey Rick—Before I answer your question, let’s talk about the functions of the receiver-drier. The receiver-drier has three functions in the a/c system.

    First, it acts as a storage tank for excess Freon.
    Second, it has filter to remove small amounts of garbage from the A/C system.
    Third and foremost, it removes moisture from the system.
    Moisture can cause a number of problems to the A/C system. It can attack the lines and corrode them. As with all liquids, water does not compress and it takes up space in the system. The compressor has 2 sides, the intake and discharge. The intake draws in Freon from the evaporator which is compressed and discharged to the condenser where the interior heat  is absorbed from the inside of the vehicle and is dissipated.
    Water in the system will not allow the Freon to compress to its fullest and therefore not all of the heat will be released.
    In other words, it does not cool very efficiently. Water in the line can also find it way to the steel bearings in the compressor and cause them to corrode. Ever heard a bad bearing?
    So, to answer your question, I would replace the receiver drier if the system has been open for a period of time. Here’s a diagnostic tool: If both the low and high side manifold gauges read normal, but the center vent duct is warm, this is a good indicator that there is water in the system.

Hey Toby—What would happen to an A/C system that has too much Freon added to it?
    —Ingred from Redondo Beach
Hey Ingred—Too much Freon will cause the system to run warm. You can check this by hooking up the manifold gauges and checking the pressure. If both the low side and high side numbers are higher that they are suppose to be, this is a good indicator that there is too much Freon in the system. If both the manifold gauges have lower numbers than recommended and there is warm air at the center vent, this might indicate that the system is low on Freon. Hope this helps.


Hey Toby—How many different types of A/C condensers exist today?
        —Rick from Norwalk
Hey Rick—There are four types of A/C condensers:

One note—you should always match the same type of condenser that came with the vehicle. I have seen where a tube and fin design was substituted for a parallel flow and cause all kinds of overheating problems in a Honda.

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