Window Fogging

["R. Cummings" <cumm@flash.net>]

I'm not familiar with the hardware on that car but I'll give you the theory.

If you operate in recirc you will fog the windows because you are not
removing the moisture from the vehicle. The symtoms of severe fogging under
40 f supports this as this is about the temperature that the compressor will
not run so moisture will not be condensed on the evaporator with the
refrigeration system operating.

The best way to tell the difference in modes is as follows:

Run the engine at idle with the A/C blower on high. Switch back and forth
between outside air and recirc. In one of those positions the noise will be
louder and noise will come from the passenger side under the IP.

This position is recirculation. The reason for the noise increase is that
you open an air path from inside the vehicle to the blower inlet. You can
then hear the blower noise in the passenger compartment.

You should always run in outside air mode unless you need maximum cooldown
performance. I assume you mean the evaporator was changed when the system
was serviced. This probably required removing the air inlet with the recirc
door.

There are a couple of possible problems. It is possible but unlikely it can
be hooked up backwards. The door may not be working. There could be a
blockage in the outside air path. Drive down the road in vent mode, outside
air, blower off. Does ram air come out the outlets. If not, the outside air
path is blocked or you are stuck in recirc.

It is not unusual to experience fogging on startup when the system is
working properly under the following conditions:

During the day the temperature is above 40f and damp and you drive with the
compressor running (A/C or defrost mode). The evaporator is condensing
moisture. You park overnight but the evaporator stays wet. You start up in
the morning when it is below 40f and the air flow blows the water off the
core and onto the windows. The compressor doesn't run because the ambient is
too cold.

Another possibility is that the evaporator drain is partially plugged and
the condensate cannot drain. Do you get water on the floor? If so clean out
the drain to the engine compartment.

That's it, good luck

Bob Cummings  87 Coupe GT