Posted 07 October 2004 - 09:34 AM
Mould, mildew, and sudden spontaneous windshield fogging over.
These problems have been with us since A/C began to be used, but became dramatically more prevalent with the advent of the use of the new, less efficient, refrigerant.
When the LS400 was first introduced in 89 the A/C design was already r-134 compatible.
Basically that meant a much greater complexity, density, for the A/C cooling evaporator, 10,000 square inches in the LS versus 4400 in an 84 T-bird. Another means to improve efficency was to dramatically reduce the cabin atmospheric outflow. The idea being that once the cabin atmosphere is cooled don't let it escape very rapidly. This last bit obviously had a positive effect on the fuel economy as now the A/C need not cycle on as often. The other result from more thoroughly sealing the cabin from outflow is that the system blower can be run at a much lower speed (less fresh air inlet) thereby improving the efficiency of the system to even a greater extend. The longer it takes the air to more through the 33F evaporator the colder it will become.
So here we are in 1990, 91 with a SUPER efficient A/C system in preparation for the use of r-134 but the factory is still filling it with freon.
Soon customer complaints start to come in about horrid A/C smells and sudden windshield fogging. So lexus decides that the odor problem can be overcome by coating the evaporator surface area with a porous nylon film into which is embedded an anti-microbial chemical to prevent the inordinant grown rate of the microbes that comprise the "family".
Then things start to really go WRONG!
First, they over-looked the Fed's requirement to file a form (MSDS??) acknowledging the use (and testing"") of a chemical fungicide to which ALL passengers in their vehicles will be exposed. And second, they completely overlooked the fact that with repeated "washings", daily use and non-use of the A/C, the result of which the chemical was quickly "leached" from those pores.
That, of course, resulted in the porous surface now acting very much like a huge sponge, absorbing the moisture condensed on the evaporator and retaining it for much longer periods than would be normal. About a pound of water over a week of exposure sitting by itself, open, alone, in a closed two bay garage.
And because that porous nylon film was created by human designed manufacturing process the pores themselves turned out to be of a fairly consistent size and/or volume.
Those of you who are schooled in atmospleric sciences and have an understanding of "vapor pressure" are probably well ahead of me at this point.
The suddenness of the complete and spontaneous fogging over of the interior surface of the windshield that many owners started experiencing with the arrival in the marketplace or the 92 model was directly related to the initial use of the nylon film containing the fungicide.
I probably have the only existing copy of any Lexus documentation indicating the illicit use of the fungicide for that short period during late 91.
So, the horrid odor of the out-gassing of the microbial spores breeding every night in 60-70F dark, dank and DAMP atmosphere of the AQ/C evaporator has been with us since the advent o fthe use of A/C. But the neeed to improve the efficiency of the system for the use of a new much less efficient refrigerant has obviously led to the horrid dirty gym socks odor being more pronounced and prevalent.