Musty, horrid, foul smell from A/C

wwestwwest Member Posts: 10,706
edited March 2014 in Lexus
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Has anyone out there used a UV light mounted within the A/C evaporator plenum to prevent the growth of mold and mildew?


  • bburton1bburton1 Member Posts: 395
    Forgetaboutit. I sell these things to hospitals and they have to work within a very narrow wavelength to provide any benefit at all. Have seen these things installed on very large hospital HVAC systems and we get a call and ask why is all that mold growing on our coils. Well they tested it with the system off but when cold air is pouring over the bulbs-they do not reach the right temp. Mold is bad stuff-try to scrub the coils with bleach. Mold won't grow unless there is dirt and moisture. You can get rid of the dirt but moisture goes with the device.
  • wwestwwest Member Posts: 10,706
    for the input on UV...

    So the only answer for our cars, really, is to find a way to thoroughly dry out the A/C evaporator (sponge) during the times when the vehicle is not in use.

  • opera_house_wkopera_house_wk Member Posts: 326
    I have heard this works well but haven't tried it myself. You can also use a spray bottle to mist the air intake when the blower is on. It is very important to check the condensate drain tubes for blockage or else the problem is back very soon. A friend of mine had a Jeep Grand Cherokee and there was a recall for that reason. They forgot to drill the drain hole at the factory. That got fixed but his message center never worked after that.
  • brorjacebrorjace Member Posts: 588
    I know it's not a perfect/ideal fix but I use Lysol spray introduced to the running fan through the openings at the bottom of the windshield. (vents must be open)

    It's important to keep the outside air open as much as possible when running A/C and to prevent excess condensation, turn the compressor "off" and leave the fan "on" for the last 3-5 minutes of your trip.

    --- Bror Jace
  • wwestwwest Member Posts: 10,706
    That's exactly the procedure I had a friend use today, he just bought a used 98 LS400 that was brought up from Tucson (Ptld, or).

    But I would advise those that have garages to leave the sunroof and windows open in the garage to let the car dry out. That worked for me back in 93 when I first came to realize why my LS400 windshield was fogging up on cold mornings about five miles from home.
  • wyncotewyncote Member Posts: 5
    My Ford Ranger, bought new last summer, has had the musty, mildew smell problem since the first week. It would come and go and seemed worse on damp/rainy days. My big problem is not the smell, but whatever is causing it makes me very sick when I run the blower, esp. the AC.

    The dealer deodorized it twice (no help) then said they had to pull the dash and replace the evaporator. But they later copped out as he tech. couldnt duplicate my concern. I went to another dealer who said they are well aware of the problem ... they had a service bulliten or something on it ... and they would need to replace the evaporator. They too ended up not replacing that (they told me that didnt apply to my truck) but installed what the service writer described as a "reverse fan" to prevent the smell's return. I told him the smell was not the big issue but whatever was causing it, is making me sick. I asked him if this would solve that problem and prevent that cause from returning. He was very evasive and just kept telling me that they did the repair that Ford recommends.

    When I got my truck back, there was a pre-printed flyer inside stating: "A module has been added to turn on the blower motor for two minutes after your vehicle has been parked for 45 minutes. This will help prevent the return of odors from the AC system."
    So far no odor, but I still get very sick whenever I run the blower and/or AC. Is the dealer being straight, or is this being used as a "mask" for a deeper probem? Thanks
  • spokanespokane Member Posts: 514
    The module that operates the blower briefly following A/C use is a legitimate step in the right direction. It will help dry the evaporator and reduce the chance of mildew/mold growth. This feature may or may not be sufficient to stop mold growth. However, it seems that your system still has some mold spores in it - even though there may be no more of them growing. Some people are extremely sensitive to particular molds. Perhaps someone (not yourself) could remove some of the ductwork and use a compressed air hose to blow out the A/C housing, heater core and housing, and as much of the ductwork as possible.
  • opera_house_wkopera_house_wk Member Posts: 326
    It isn't even necessarily the active mold you are reacting to but the chemicals they may produce. Even when new production of mold stops from the blower fix, you need to wash out what mold is there. Perhaps some company that specializes in AC work is experienced in inserting probes and washing down evaporator systems without complete tear down. An environment making you sick can be a terrible thing. My new neighbor bought the house next to me. They did a bunch of fix up including new windows. A year later they tore the house down and put up a new one because the mold made his wife sick. This is river front property and they loved the location.
  • wwestwwest Member Posts: 10,706
    The smell, odor you're getting is not the mold itsself but their "leavings", the stuff you and I flush. Now that the evaporator is being "dried" it is unlikely that more effluient will be generated. But each time you operate the A/C more moisture is condensed, re-wetting the "stuff" that's already there and then of course the smell returns.

    My suggestion. Turn the blower up to MAX, make sure the system is NOT in recirculate, open all of the windows so the blower has no back-pressure.

    After its run this way for about ten to fifteen minutes start spraying a can of lysol into the intake ducts most usually at the bottom of the windshield. Do not emplty the can all in one burst use about five each about ten minutes apart.

    Let the blower run this way for at least 30 minutes after the lysol is exhausted.

    If you have an A/C air filter then remove it before the procedure.

    Most A/C evaporators these days are very dense and complex for two reasons, the new R-134 refrigerant is now as efficient and some idiot has decided to continue the use of the A/C to prevent and remove windshield condensation below 50F where it efficiency for this purpose is extremely questionable.

    In my Lexus vehicles I remove the A/C compressor clutch relay in the wintertime so this moisture doesn't accumulate in the A/C evaporator "sponge".

    In our northern climate the trapped moisture isn't so much a problem with mold breeding but random windshiedl fogging "surprises".

    Oh, and even with that blower that runs automatically you might want to leave the windows open slightly to allow the "moisture cloud" to escape the cabin entirely. Another way they have improved the efficiency the the A/C is by severely restricting the amount of cabin "exit" airflow.
  • wwestwwest Member Posts: 10,706
    I found another possible solution today.

    It's from Biozone, a UV light source in a plastic module with a small (Pentium) cooling fan to move air through it.

    Now just how do we go about mounting it in the A/C evaporator chamber.
  • jgmilbergjgmilberg Member Posts: 872
    For those interested in getting this problem fixed in your GM car/truck, here is the TSB for that issue, print it up and take it to the dealer, or at least write down the tsb number for reference.

    Air Conditioning Odor (Install Kit) #99-01-39-004A
    Air Conditioning Odor (Install Kit)

    1993-2002 Passenger Cars

    1993-2002 Light & Medium Duty Trucks

    This bulletin is being revised to update the model years, service procedure, parts information and to add the GEO and Medium Duty models. Please discard Corporate Bulletin Number 99-01-39-004 (Section 01 - HVAC).

    Some customers may comment on odors emitted from the air conditioning system, primarily at start-up in hot humid climates.

    This odor may be the result of microbial growth on the evaporator core. When the blower motor fan is turned on, the microbial growth may release an unpleasant, musty odor into the passenger compartment.

    There are several other possible sources of a musty odor in a vehicle. A common source is a water leak. Follow the Service Manual procedure for identifying and correcting water leaks if other odor sources are found. The procedure contained in this bulletin is only applicable if the source of the odor has already been determined to be the HVAC module.

    To remove odors of this type, it is necessary to eliminate the microbial growth and prevent its reoccurrence. To accomplish this, the following steps must be completed:

    1. Apply evaporator core Cooling Coil Coating (Aerosol 6 oz), P/N 12377951 (AC Delco® 15-102) (in Canada, use P/N 10953503) or Cooling Coil Coating Kit with Extension Nozzle, P/N 12346391 (AC Delco® 10-120).
    2. Refills are available for the Cooling Coil Coating Kit with Extension Nozzle, P/N 12346391 (AC Delco® 10-120). Refer to the chart below. Install the Electronic Evaporator Dryer, P/N 12497910 (AC Delco® 15-5876).


    The Cooling Coil Coatings listed above are the only GM approved products for the disinfection and long-term control of evaporator microbial growth.

    The Cooling Coil Coating will disinfect the evaporator core and help inhibit the growth of future mold and mildew.

    The Electronic Evaporator Dryer will activate when the ambient temperature near the module is above 16° C (60° F) when the vehicle is started up. Approximately 30 minutes after the vehicle has been turned off, the blower will activate for 10 seconds every 10 minutes for 2 hours unless the vehicle is restarted. If a restart occurs, the Electronic Evaporator Dryer module will reset automatically. This on/off blower activation will dry the evaporator core and case reducing the chance of reoccurring A/C odor. The Electronic Evaporator Dryer is self fused and has a battery rundown protection feature that inactivates the dryer if voltage drops below 12.5 volts.
    Service Procedure

    1. Visually inspect the air conditioning evaporator drain hose for obstructions and/or working condition.
    2. The cooling coil coating fluid must be applied to a dry evaporator core. Apply coil coating fluid as described in the instructions supplied with the kit. In some instances, the blower motor resistor can be removed for this spraying operation. If used, the opening can be taped over and the nozzle inserted through a hole in the tape. The kit instructions identify a drilling procedure to apply the coating fluid. When using this type of procedure, care must be taken to avoid evaporator damage and any holes must be properly sealed. Some coating fluid may overflow from the drain hose.


    When installing the Electronic Evaporator Module, you MUST use the included electrical splice connectors to ensure a proper splice.
    3. Complete detailed installation instructions and wire connectors are supplied with the Electronic Evaporator Dryer. The ground wire should be attached to a body ground source. If any other wire splicing procedures are needed, follow the wire repair procedures in the Electrical sub-section of Body & Accessories in the appropriate Service Manual. If required, the evaporator dryer can be installed underhood away from extreme heat conditions (i.e. exhaust manifolds) and/or water splash areas. In all cases, the evaporator dryer module must be secured with a Velcro® strip (not included in the kit), or you may use the integral hooks to utilize tie straps. Using a Velcro® strip is preferred as the use of the integral hooks may cause rattles.
    4. When the installation procedure is complete and power is supplied, the module will self-test. Thirty seconds after power is supplied, the high blower speed will be activated 3 times (for 2 seconds per cycle). When the test has run, install the Electronic Evaporator Dryer label on the blower motor case in a visible area.
  • wwestwwest Member Posts: 10,706
    For those of you to whom the TSB does not apply the module GM uses is at:

    The sad news is that none of this works for those of us in northern climes where the "trapped" moisture intermittently and spontaneously causes windshield fogging.

    The EED device is strictly to combat mold and mildew growth and doesn't work if the A/C plenum temperature doesn't rise above its trigger point.

    Other news of concern:

    Evaporator "coatings".

    Lexus did this in the 92 LS400, applied a porous nylon film to the evaporator vanes into which was embedded an antimicrobial chemical.

    When I inadvertantly got my hands on a copy of the "spec" Lexus moved heaven and earth disavowing that it ever existed and they would neevr do such a thing. At about the same time the dealers were using some third party spray to try and combat the problem.

    Turned out neither of these chemicals were approved for human "consumption", the spray disappeared quickly from the marketplace and other than the Mazda in Australia I have heard no more about antimocrobial coatings. Be very careful what you coat your evaporator core with.


  • bburton1bburton1 Member Posts: 395
    Don't want to rain on anybody's parade but I have seen commercial UV installations that do not function simply because the UV light does not operate correctly. This is hard to get right if you spend thousands of dollars on these systems. The UV light must operate in a very narrow wavelength. When it does-boy does it work. Oh also properly working UV lights will DESTROY human retinas in a very few seconds. I have seen mold actually growing on some commercial UV installations. However when they work, the slime/mold goes away in a few days.

    Having said all that I hope these things work and if they do-protect your eyes.
  • wwestwwest Member Posts: 10,706
    Porsche factory tech rep told me last week that the reason almost all automotive manufacturers continue to operate the A/C compressor all the way down to absolute minmum, functional temperature, 32F, is to keep the mold and mildew odor down to a minmum level.

    It does make sense, I'm sure it works, but seems a terrible waste of energy.
  • swschradswschrad Member Posts: 2,171
    if the energy cost is acceptable to you (you don't get hyper and unplug the clutch coil on the compressor, so it can't be put into service) it ain't a waste.

    the next guy over is a nut and doesn't count ;) that's what the market teaches us.

    until all affiliated costs of using energy are reflected in the price tag of that energy, goes the other side of the argument, the market is hogtied in the corner and isn't teaching anybody anything.

    pick your side, start a new topic, and argue away. the automakers will keep using the compressor and its 5-8 percent reduction in mileage, until the market says stop.
  • wwestwwest Member Posts: 10,706
    Actually, on my RX300 I do remove the compressor clutch relay in the wintertime. Don't drive the 996 in the wintertime enough to bother, just try to remember to turn it off each time.
  • swschradswschrad Member Posts: 2,171
    does make it difficult to run the compressor monthly, as the advice has gone for years, to keep the seals lubricated and prevent leaks, etc.
  • wwestwwest Member Posts: 10,706
    is worth what you pay for it.

    Running your A/C compressor once a month is not a bad idea, but I have had no negative results in 30 years of owning cars with A/C by NOT.
  • corvettecorvette Member Posts: 10,047
    Looks like this is the only A/C topic on the Maintenance and Repair board, so I'll go ahead and ask here rather than creating a new topic. The A/C on my friend's 626 quit working. I assume this was the first time she tried to run the A/C since winter. The climate controls work fine for blowing hot or tepid air, and when you press the "A/C" switch, you can feel a pull on the engine, just like any other car. Just so you have all the relevant info, I suspect that in 45,000 miles, this car has seen little maintenance other than infrequent oil changes. Does the fact that I feel the engine lug a little indicate that the compressor is okay? Or is it possible that she needs a compressor (expensive repair)?
  • swschradswschrad Member Posts: 2,171
    typically, a probe thermometer in the dash outlets reading higher than 50-odd degrees in max cooling (there are tables to adjust for multiple outside temperatures, to be exact, but I'm talking what you can try now with a cheap thermometer and without a court order) indicates that there isn't any cooling (might have to put a big-[non-permissible content removed] industrial fan in front of the radiator if the car gets any warmer than usual on the coolant temp gauge.) if the engine lugs, the issue isn't the compressor. so the likely culprits, as usual, would be insufficient refrigerant, loopy regulator valves, and/or water in the pressure system. diagnosis of that requires the gauge set... and of course, under Federal law these days, the tech wielding the tools and doing the work having the appropriate EPA training, equipment for coolant recovery and reuse, and license.
  • corvettecorvette Member Posts: 10,047
    Thanks, swschrad. I will pass the info on, and be suspicious of anyone trying to sell her a compressor. Thankfully, I wasn't expecting to fix it myself. :)
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