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HEATING
For maximum heating (with warmed engine), control should be as follows:
1. Driver’s heater fan switch—“Hi.”
2. Main (dash) fan switch—“Hi.”
3. Main (dash) heat lever—“On” (see DEFROSTING).
4. Heater booster pump—“On.”
5. Water regulating valve—max “red.”
6. Rear heater fan switches—“Hi.”
7. Fresh air flow control—“Pushed to the right for maximum efficiency.”
Caution: Without this in maximum fresh air position in cold or very moist weather conditions,
windshield may fog up.
As interior warms up, heat can be regulated by one or more of the following:
1. Turn water booster pump to “off.” Note: Must be “off” if water flow valve is not in full open position.
2. Reduce water flow through all heaters by turning water regulating valve clockwise (toward all “sil-
ver”).
3. Lower heater fan speeds.
4. Reduce dash heater air flow by pushing main heater temperature control to the left and leave wind-
shield defrosting at maximum
NOTE:
The heater booster pump will give maximum water flow through the heaters. It should not be used
when the water regulating valve is partially or completely closed.
HEATER ACCESS
1. Front Heaters—The front heater can be accessed from the inside of the bus on the dash near the
stepwell. To gain access to the heater core and filter from the interior of bus, remove the interior
heater access panel.
NOTE:
The armrest on the right front seat may require removal to improve access to the heater panel.
2. Rear Heaters—To gain access to rear heater, the following procedure should be used.
Remove seats over heater.
Remove top heater cover.
Remove heater tie-down screws.
Remove heater from floor, pull it away from the wall and remove hose connections.
Disconnect motor wires and remove heater from bus for further disassembly.
FILTER
The main heater coil is protected by an air filter. The purpose of the filter is to prevent dirt and dust from
collecting on the heat exchange surfaces and lowering the efficiency of the heater. The filter can be cleaned or
replaced by removing the return air/filter access panel. The service frequency of the filter will depend en-
tirely upon the operating conditions of the bus and care should be taken to keep it cleaned. A dirty filter is
restrictive to air flow and reduces maximum heater output.
DEFROSTING
Windshield fogging and frosting is caused by warm, humid air coming in contact with a cold windshield,
which causes the moisture in the air to condense and possibly freeze if the windshield is cold enough. The
warmer the windshield, the less moisture will condense on it. During initial warm-up, the defroster blowers
should be operated at low speed to preheat the inside of the windshield glass. If the defroster is not turned on
until the condensation starts, it is more difficult to heat the glass and overcome condensation. As passengers
are loaded onto the bus, the moisture content of the air inside the bus increases. This moisture content tends
to be lowered by opening the heater fresh air inlet. The most difficult defrosting conditions will be encoun-
tered when there is a large passenger load which must remain on the bus for extended periods of time, such
