Volvo VHD - Manual (Page 178)

172 Heating and Air Conditioning
Fresh Air Control
The top slide lever is the Fresh
Air/Recirculation Control. The settings can
be anywhere from full fresh air intake to
only recirculated air. Settings can be chosen
anywhere in between to give the desired
flow of air.
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In the leftmost position, the
fresh air inlet is closed. All air
is recirculated within the cab. It
can be used to heat up or cool
down cab temperature quickly
or to close intake from letting in
odors, etc. with the intake air.
In the middle position, there will
be a 20% addition of fresh air
to the 80% of recirculated air.
This position is well suited for
use when the air conditioning is
engaged so a minimum of warm
or cooled air is lost through the
evacuation vents, while fresh air
is still added to the cab.
In the rightmost position, the
fresh air inlet is completely
open. This is best used when
heat is required (wintertime)
and when defrosting or de-icing.