willard west

My new 1992 Lexus LS400 came to me with a special Lexus "feature", one that to my knowledge I had never encountered before.

The air conditioning evaporator, heat exchanger, was coated with a fine porous nylon film into which was embedded an Anti-microbe chemical.

Apparently it was an effort by Lexus to eliminate or at least retard the growth of mold and mildew spores in the damp and dank environment of the A/C plenum area containing the complex and dense evaporator structure appropreate to a luxury sedan.

Over the past ten years I have noticed a great number of posts on various automotive forums on the internet complaining of a "musty smell" or the "dirty sock syndrome" emanating from the vehicle's A/C outlets. There also seems to be a great number of posts regarding the frustration of dealing with windshields that suddenly fog up or cloud over, especially in the early morning. I myself have been VERY frustrated over owning various Lexus models over the years, Bill Gates' 90 LS, my 92 LS, a company 95 LS, a 2000 GS300, a 2000 RX300 AWD and a 2001 RX300 AWD. ALL having the propensity to spontaneously, completely and totally unpredictably, suddenly fog over the entire interior windshield surface.

Just recently I noticed an aftermarket product designed to combat the formation and growth of mold and mildew in the automotive evaporator plenum environment. It's description and purpose is worth a read...

http://www.airsept.com/eed.html

But how do you go about eliminating the mold (possibly even TOXIC mold) and mildew growth and eliminate the extremely hazardous circumstances of windshield fogging, spontaneous are simply repetitive early morning occurances?

My recommended solution to you Lexus owners is much less expensive to implement and will take about ten minutes of your time twice a year.

As wintertime approaches, once the average overnight outside temperatures have declined below about 55 degrees F, remove the A/C compressor clutch control relay and store it away for safe keeping to be reinstalled the next spring when the actual need for A/C cooling returns.

The A/C indicator on your dash will flash on and off, indicating that the A/C compressor is not turning in synchronization with the engine. You can use that flashing as a reminder to reinstall the relay when the time comes, or you can cover it with a small piece of electrical tape if it annoys you.

With no moisture (well, virtually none) being accumulated on the evaporator vanes during the cold winter months when it will not readily evaporate away during the night, you will not have need to worry regarding mold and mildew growth.

And guess what?

A REAL bonus, there will be NO "surplus" moisture available to coat the interior surface of the windshield when you first start the vehicle up in the cold early morning hours.

AND... You are now free to use the defrost/defog/demist function without fearing the return of the dreaded moisture TIME BOMB.

If the A/C compressor were working in this mode it would cause a great deal of moisture to be accumulated on the dense and complex evaporator surfaces and now you would be TRAPPED in the defrost/defog/demist mode FOREVER. Or at least until you can somehow remove the condensed moisture from the thousands of square inches of evaporator surface without having it evaporate back into the incoming airstream and start the initial defrost/defog/demist process all over once again, and again, and again.....

Now you will rarely have need to defrost/defog/demist the interior surface of the windshield or windows. But when you do the proper procedure will be the old time tested , and well proven one, activate the defrost mode, but simultaneously turn up the heating setpoint to lower the relative humidity enough to accommodate a "state change", the moisture condensed onto the windshield is in a liquid "state" and you need to "boil" it off, change it to a gaseous "state".

In a Lexus, once the cabin atmosphere has acclimated to the system setpoint, say, 71 degrees F, the climate control system airflow temperature to the interior surface of the windshield temperature level will be, predominantly, about 66 degrees F, and with four full grown passengers it might be as low as 50 degrees F. When you switch the mode to defrost/defog/demist, there is NO input to increase the airflow temperature level to the windshield, so you must do this manually.

The old saw, "An ounce of prevention is worth a pound of cure" still holds true.

Lexus correctly uses the A/C compressor, "an ounce of prevention" to PREVENT fogging of the windshield, but they neglected to remember the "pound of cure" once the windshield condensation is fully formed as a result of the windshield itsself having been CHILLED to the dewpoint of the surrounding atmosphere.

Once condensation has formed on a cold interior windshield surface it will take more than a "pound of cure", it will take something on the order of a "sledgehammer" to force a "state change" in the chilled liquid held to the windshield by its own viscosity.

HEAT!

eppan

Interesting post...although damn long.

I looked at your link...and it is an interesting device. It seems to be useful for those who do not do it manually. I personally, turn off my A/C a few miles before reaching my destination in the summer time, that way it forces outside air through the system. Also, in the winter time if used as a defroster... I would force warm/hot air through after using the defroster with A/C.

That is my practice...and it works like a charm...never had any rotten egg/mildew smell.

Also, somewhere I have heard that even if you do not use the A/C you should turn it on once in a while to keep the A/C seals lubricated. Interesting enough...my A/C in my '89 toyota never needed recharging (nor does it leak). Can not confirm that turning it on once in a while through out the years helped but I am certainly happy that no maintanance is required.

wwest

In the wintertime if I used it as a defroster ---- I would force warm air through it afterwards.

Unlike LA, here in the Northern reaches we don't have a ready source of warm air in the wintertime.....

The article applies, predominantly, to areas that have sub-55 degree F average night time temperatures that persist for weeks on end. I wouldn.t exactly call LA a humid enviroment either.

eppan

Cool! Ya...no problems over here...although if people don't take care of the A/C the moisture will buildup and smell like rotten eggs.

Mean Gene

Epp - It's not only a good idea to run the A/C once or twice a month in the winter to keep the seals & O-rings lubricated but also to do the reverse in the summer. That is, run the heater occasionally to remove any condensation that may accumulate in the heater core & can lead to premature rusting out ( although not as severe a problem with today's metallurgy ). Of course, I'm like yourself - don't keep a vehicle long enough to experience some of the more longer term problems such as these.

Goods

You had Bill Gate's '90 LS?
Am i the only one who caught that mention?

willard west

Bought it from the dealer, gave it to a friend/business associate in Ptld, he Gave it to Outward bound for a charity auction, then it was next auctioned for the humane society.

Last I knew some bank on the East coast was trying to sell it on Ebay for $40,000 plus.

AmanO

This is, probably, my worst necro, yet, but.....

This opinion needs to be offered.

STOP KEEPING YOUR CYCLE ON RECIRCLE!.

I bought an 01 and I would bet a decent amount of my savings that the lady (I can tell as the center console compartment smells like perfume) that drove it before NEVER had it on fresh. As SOON as I turned it on fresh, I smelled mildew/mold. I have since switched it back and forth and either the smell has dissipated or my brain deems it as normal. I doubt that as it was not a lingering smell like my rubber floor mats. I can tell my brain adjusted as after I bought my GS, I did not drive the Camry for a couple weeks. When I got back in, the rubber smell hit me in the face like the day I bought the mats.

There is a reason there is (or should be) a cycle switch in cars. I see no reason to run on recircle much at all in the winter. Using heat does not affect mileage and the outside air is generally dry. (At least in the midwest)

In the summer, you should start with which area is cooler. Here, that is usually outside because of the greenhouse effect. Then switch to recircle when you are at temp. That way the system either can run less (if auto) or at a lower fan speed/temp if not. The systems work on a thermostat, not a hygrometer, so intaking the dryer air does not help as much as the cooler air.

TL;DR Using the fresh cycle on a regular basis will keep that ductwork freer of mold/mildew and smelling better.