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Toyota Avalon Climate Control Questions



  • mdealmdeal Posts: 2
    I too am having problems changing out a air filter on my 2000 Avalon
    Bought one from auto parts store & the directions that came w/ it
    are diffrent than my year.Instead of a phillips screw for the glove box stop,it
    is some type screw you have to line up w/ a slot to remove.Any help
    would be great.
    Thanks MIke
  • rsh1rsh1 Posts: 1
    My husband and I purchased a 2007 Toyota Avalon Ltd in the fall of 2006; overall we are extremely pleased with the vehicle. However, there is a foul smell coming from the air vents when a/c or outside air is on. The dealer says that the recommended fix is to simply spray lysol into the vents from under the hood. Seems to me that only masks a deeper problem. Anyone have this problem?
  • tjc78tjc78 JerseyPosts: 5,025
    The dealer is right. There is most likely a touch of mold in the ducts. The Lysol will typically cure it.

    1999 Chevy S10 / 2004 Merc Grand Marquis / 2012 Buick LaCrosse

  • amauhryamauhry Posts: 55
    Kill the fungi first (any bacteria disinfectant spray may do the trick). If left alone, your situation will reoccur, and then you’ll have to spray more Lysol again.

    Long-term solution: right after using the AC on hot & humid days you should run the blower (AC off) at high speed and in heat mode for about 2 minutes. Use “outside air” mode; not the “recirculated” mode. This will dry the ducts and evaporator fins and coils leaving no room for mold and mildew to grow.

    '08 Limited
  • wwestwwest Posts: 10,706
    Contrary to the above, it will take at least 10-15 minutes, typically, but up to an hour to raise the temperature of the 10,000 square inches of evaporator vane surface area enough to have the remaining thin film of moisture thereon begin to evaporate into the airstream. The operational "target" temperature of the evaporator is ~34F.

    Absent modifications to the system your best bet is to leave the windows down slight each and EVERY night provided the car is under shelter.

    For a really viable modification go to:

    And read up on their EED, Electronic Evaporator Dryer.
  • wwestwwest Posts: 10,706
    The heater core is ALWAYS downstream of the evaporator core so it does no good to turn up the heat when attempting to dry the evaporator. And just how long it will take for the thin film of moisture to begin to evaporate off of the near freezing evaporator vane surface area is a function of the outdoor climate. Your 2 minute "estimate" would imply an OAT of >100F and an Rh of <20%

    And this "condition" is not restricted to HOT and Humid days, most modern day climate control system run the A/C all year around (primarily for dehumidification during the heating seasons) and so the evaporator vanes can be literally "choked" with moisture at any point the A/C is switched off.

    The growth of the microbes leading to the "dirty gym socks odor" is primarily between 60-70F in a dark, moist, "dank" environment. Say in your heated garage at night in the dead of winter.
  • mashoudmashoud Posts: 8
    The Avalons are notorious for Heating and Cooling problems and if you write to Toyota, you would not even receive a reply.
    As for the "fungal' problem and the stench, it is more likely that the interior cabin filter is plugged tight with pollen and debris and the stench starts there.
    I would change the filter which is located just under the glove box.
    You would find it black with moss and slime from the moisture.
  • wwestwwest Posts: 10,706
    "Avalons are notorious..."

    As are LS400's, RX3X0's...

    In point of fact almost all passenger cars of asian origin since they primarily use HVAC designs, horribly FLAWED HVAC designs, by NipponDenso.

    I think I have read that the newer LS430's have a UV light inside the A/C plenum to belay/retard the growth of these microbes.

    Even worse, many US marque are now also suffering, due to this design flaw, as a result of the presence of NipponDenso in our shores as Denso US.


    Pollen filters undoubtedly help to prevent the formation of mold and mildew spores/microbes through denying them the "food" they need for growth. That isn't to say that an overage pollen filter wouldn't be a heavy contributor to bad odors.
  • amauhryamauhry Posts: 55
    Forgot to mention that for an effective killing, the bacterial disinfectant must be sprayed in the evaporator area (the entire core), since this is where most of the fungi are located.

    This also means that you have to do some "digging" in order to have access to the evaporator.

    '08 Limited
  • amauhryamauhry Posts: 55
    I haven&#146;t yet seen an HVAC system where the heater elements follow the evaporator coils. I have taken apart my own house HVAC (forced air, upright setup) where the heating elements (heat exchangers by natural gas) PRECEDES the evaporators coils and fins of the refrigeration cycle. This OEM setup is not pure coincidence; the HVAC manufacturer is using the heating season to kill a potential house problem, which could easily develop during winter under the coziness of a non-conditioned equipment room located in a cold, damp basement. True, during winter I know that the air is dryer (I have measured 24% rh in my house; I keep a well-calibrated hygrometer, with NIST traceability, in my basement), but I&#146;m aware of damped basement here in NYC during winter.

    I do not doubt what you&#146;re saying about the arrangement of the heater and evaporator in a car&#146;s HVAC, but I haven&#146;t seen it yet. If you could prove that your arrangement is the rule-of-thumb for car&#146;s HVAC (schematics for example), then I will learn something new and shut up.

    I have never, ever have a problem with foul smell in any of the car I&#146;ve owned because I practice what I&#146;ve explained earlier.

    &#146;08 Limited
  • amauhryamauhry Posts: 55
    My hat&#146;s off for you wwest. Indeed, I looked at the HVAC system diagram for the Avalon &#146;08 and the heater core is downstream of the evaporator. They do share the same compartment however. As I said earlier, I never saw this arrangement before since I&#146;ve never experience HVAC issues with any of the cars have owned so I have not had the need to explore this field (in cars) with details, and that prompted me to not disregard your theory completely.

    Is this the de facto arrangement for all cars? I do know that my practice of running the heater has saved me from smelling bad odors stemming from the air vents ; perhaps because of different configuration? Or because these two units are next to each other in the same compartment hence sharing the same air volume?

    Again, thank you from making me dig some info &#147;new&#148; to me.

    BUT let me tell you that your recommendation of leaving the windows down makes
    sense only IF each and every night the RH of air is about 60% or below; otherwise, with high RH values your suggestion won&#146;t work. And I&#146;m sure you know that is very difficult to get those 60% or below RH values outdoors during the summer season. Also the 34F temperature at the evaporator coils is more of a design value than an actual value. My house HVAC with a SEER of 15+ has always measure an average of 40F at the evaporator (with identical indoors temperatures and wet-bulb temperatures)
  • wwestwwest Posts: 10,706
    Sorry, I would have said "automotive" HVAC systems had I known the post was that open to (mis-)interpretation. And if you can figure a way for an automotive A/C to be used efficiently for dehumification with the evaporator downstream of the heater core I'll pay for the patent attorney.

    "If you could prove..."

    I have no need to go "there".
  • wwestwwest Posts: 10,706
    Wow, you're giving me a lot to answer "for".

    Not long after you shut your car off in the evening after a day of A/C use the HVAC plenum area will rise to EXCESSIVE RH, possibly into the level of SUPER-SATURATION. The idea is to let the passenger cabin acclimate to the "local" Rh, not leave the elevated RH or super-saturation condition exist overnight, night after night.

    And your home HVAC system DOES NOT have a thermistor mounted on the evaporator downstream surface to prevent the controller from allowing it to go below FREEZING. If you home's system ever has INLET airflow conducive to the evaporator freezing over you have a really serious problem.

    "design value rather than an actual value.."

    No, in a modern day automotive the HVAC system is more often used ONLY for dehumidification rather than both cooling and dehumidification. During the winter months the airflow ENTERING the automotive HVAC might readily be low enough that the evaporator would easily freeze over if not prevented from doing so by the control system.

    Addtionally I rather doubt that your home system has a remix/reheat mode as does almost all modern day automotive HVAC systems.
  • amauhryamauhry Posts: 55
    If your &#147;local&#148; RH is 90% night after night, you don&#146;t need SUPER-SATURATION for fungi to grow. Any number between ~ 65% to 100% RH on a daily basis will happily support fungi life. Guaranteed.

    Why do you want my house&#146;s HVAC to have a thermistor? I&#146;m quite sure that the TXV valve my system has does the job a whole lot better and efficiently, since it monitors the Freon R22 state across the evaporator, self-adjusting the fluid&#146;s pressure (hence its temperature) accordingly.

    The remix in your &#147;remix/reheat&#148;mode is not practical for home application; first, most home are not made of glass; second, even if they were, there would be no need to instantly defog the &#147;windshield&#148; of such houses as would be in a moving car, say, during winter; third, …. Properly sized residential HVACs significantly lowers RH levels with the use of AC during the summer, and their heated, dry air &#147;dehumidify&#148; even more during the &#147;dry&#148; winter. Most residential HVACs, especially those with an SEER of 10 or higher, are more efficient than automotive HVAC&#146;s, where efficiency is sacrificed for compactness.

    About your &#147;reheat&#148; mode? Yes, my 6-ton HVAC is always in recirculated (summer) or reheat (winter) mode; I couldn&#146;t think of my electric/gas bills if this monster had a &#147;fresh&#148; air intake mode; ain&#146;t just practical for home HVACs.

    &#146;08 Limited
  • wwestwwest Posts: 10,706
    "You don't need SUPER-SATURATION for the fungi to grow."

    Even with clothes freshly out of the washer you can hang them outside to dry and the disparity between even 100% Rh and the wet clothes will result inthem being dry within a few hours.

    The point is that even 100% relative humidity does not equate to prevention of enough evaporation to reduce the level of moisture wherein the A/C plenum getting below the level in which it would support microbial growth providing even a small level of convection airflow is made available. Forced airflow, even better.

    "Do you want my house's HVAC to have a thermistor?"

    No, my point was that automotive systems, wherein absent "control" the evaporator might freeze over, your "house's" HVAC will likely never "see" that threat.

    "The remix in your "remix/reheat" application is not practical for home application;"

    Well, not only is it PRACTICAL, the remix/reheat method is currently in daily use in many homes, for the very same reason for which it is used in automobiles.

    Most are standalone DE-humidifiers but some more upscale homes actually use central heating and cooling in combination, simultaneously, to both cool and dehumidify the home and increase human comfort levels. Obviously the highest level of dehumidification would be attained with the evaporator operating at the lowest possible temperature thereby oftentimes requiring the use of the reheat/remix application/method.

    And the actual numbers, temperature range, for microbial grown is 65-75F.

    And IMMHO automotive A/C system efficiency could be quite significantly improved (along with FE) via ALWAYS using recirculate and somehow bypassing the reheat/remix mode during the cooling season when there is no THREAT of/from windshield fogging, INTERIOR windshield fogging anyways.

    During the summer months, cooling season, I always set my automotive A/C system to the maximum cooling level (it then automatically switches to recirculate) wherein the reheat/remix vane/door remains firmly SHUT, and then I manually adjust the blower speed to meet my cabin cooling needs.
  • amauhryamauhry Posts: 55
    The only one reason automotive HVAC combines heat mode with cold mode is because the driver needs that function during the not-so-often humid instances of the winter season so that he/she has clear sight through any of the car&#146;s glass surfaces as quickly as possible. In this combined mode, the A/C is used solely to remove moisture on the spot from the windshield, and the heat, though it removes further moisture, is provided mainly for the driver&#146;s comfort (remember, it is winter).

    You should know better. Air conditioning not only cools but dehumidifies (removal water molecules from the air) at the same time, or did you forget about the dripping water from window A/C units? Where do you think that water is coming from?
    In my 6-ton unit, it is a continuous flow of water through a ¾-inch black PVC pipe connected to a drain. So why the need of heat, especially in the summer, to remove house humidity when the A/C does it better and cheaper by itself? I&#146;d feel sorry for those home owners with such an option on their HVAC system not because of their wasted money (in case they&#146;re filthy rich) but because of their ignorance.

    There&#146;s no need for this combined heat/cold mode for a home, and such an option would be redundant and a waste of energy both on the cold and heat side.

    &#146;08 Limited
  • nimiminimimi Posts: 249
    Since you guys seem to have HVAC down pat, can you tell me why I DO NOT see puddles of moisture under my '08 Limited after I park the car and having run the AC?
  • tjc78tjc78 JerseyPosts: 5,025
    That is surprising... my '06 has a mini flood underneath it after I park. I live in NJ which is always that could be it. Keep an eye on it, you could have a plugged drain tube, which could cause it to overflow into the car.

    1999 Chevy S10 / 2004 Merc Grand Marquis / 2012 Buick LaCrosse

  • amauhryamauhry Posts: 55
    Minimi, because there is a hose constantly draining the water from your A/C to the outside (vehicle&#146;s undercarriage). Wanna see it? After running you A/C for some time, park your car (think safety first!). Wait less than a minute. Then take a peak underneath your car by the engine area. You gonna see the water (from the A/C evaporator) dripping + the puddle just like tjc78 suggested.

    Actually, the evaporator core has a drain pan (or condensate pan) where it collects the water from the moist air being &#145;conditioned&#146;. A hose connected to this pan drains the water to the exterior, underneath the vehicle. The design is such that water flow throughout the drain system is by gravity.

    '08 Limited
  • amauhryamauhry Posts: 55
    My apology for misspelling your user-name nimimi. Precisely the drain house should be somewhere past the engine area by the driver&#146;s area but in the undercarriage section.

    '08 Limited
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