Buick 1993 Roadmaster Owner's Manual page 134

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'Your Buick may have this
Comfort Control. System.
,
. .
.
.
.
Your Bui&'s flow-through ventilation system supplies
outside air info the vehicle when it is,moving. When the
heater
or
air c.onditioning fan is running, outside .air will
also enter the-vehicle.
. .
, .
Fan Speeds:
The fan- control is used to select
the
speed you' want the
blbwer to contrdl the:& flow.
B/L (Bi-level)
:
This setting is designed for use on s m y days'whexe the
air is only moderately warm or.-c6c?l. O n days like these,