Mercury 1999 Villager Owner's Manual page 24

Controls and features
Rear seat heating
Rear seat heating is provided through the floor ducts located under the
front seats. Airflow and temperature to the rear seating are regulated by
the main climate control system.
OFF REAR A/C 1
The rear passenger compartment air conditioning system (if equipped)
should be set to OFF, if rear heating is desired.
Operating tips
In humid weather, select
on your windshield. After a few minutes, select any desired position.
To reduce humidity buildup inside the vehicle, don't drive with the
climate control system in the OFF position.
Don't put objects under the front seat that will interfere with the
airflow to the second row seat floor ducts.
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2 3 4
before driving. This will reduce fogging
A/C