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DRIVER'S HANDBOOK
Defrosting
Windshield fogging and frosting is caused by warm, humid air coming into contact
with a colder windshield, which causes the moisture in the air to condense and
freeze if the windshield is cold enough. The warmer the windshield, the less mois-
ture will condense. During initial warmup, the defroster blowers should be operated
at low speed to preheat the inside of the windshield glass. If the defrosters are not
turned on until after condensation starts, it is more difficult to heat the glass and
drive moisture away.
As passengers are loaded, the moisture content of the air inside the bus increas-
es. This moisture content tends to be lowered by opening the heater fresh air inlet.
Conditions will be especially difficult when large passenger loads stay on board for
extended periods of time, such as on a charter or over-the-road activity trip. Travel-
ing at highway road speeds causes heat to dissipate through the windshield glass,
and each passenger's breath continually adds to the air's moisture content. To reduce
fogging, open the forward driver's window slightly to let the moist air escape. Fresh
air control knob should be set to full fresh air position (counterclockwise) for defrosting/
defogging operation.
Heater Defroster Location
The blower in the front main heater contributes to keeping the driver's area glass
clear of fog and frost. See OUTLET LOCATION diagram. For best results, fresh air
should be flowing into the heater. To inspect the fresh air intake and make sure it is
working properly, open the front access panel on the right side of bus.
Driver / Passenger Comfort
When the windows are defrosted, the other openings can be set as necessary for
comfort. The adjustable diffusers on the dash can be directed toward the driver and/
or passengers as desired. The optional auxiliary unit under the driver's seat has a two-
speed electrical switch and it directs air upward for the driver's left side and forward
around the steering column area.
Temperature Control
The temperature control knob varies the amount of engine coolant flowing through
the heater system, this directly affects the temperature output of the heater. Note:
If the bus is equipped with an auxiliary fuel-fired heater, the temperature control knob
must be set to the "Full Hot" (clockwise) position before the bus is switched off in order
to function properly.
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