[s-cars] Windshield fogs up in cold weather & AC is off

[Thomas Rodriguez]

Now that the weather is cold my windsheild fogs up when I run the
heater or defroster.  I believe this is because the AC is not
operating when the outside air temperature is cold, so it doesn't
remove the moisture from the air before it passes through the heater
core.  It is my understanding that the AC is supposed to run in the
winter expressly for this purpose.  The AC indicator light on the HVAC
control panel is unlit.  If I push the AC button on the control panel
the indicator light illuminates as long as I hold the button down, but
goes out when I release the button.  I am confident the fogging is not
due to a coolant leak into the HVAC system; I recently replaced the
heater core and there is no coolant odor inside the cabin and no drop
of coolant level in the reservoir.  The heater works great (aside from
the moisture) and the AC worked great during the summer.  Am I correct
that the AC should be operating in concert with the heater &
defroster?  Any tips on how to correct this?

Thanks,
Tom Rodriguez
'95 S6