25
HEATERS
GENERAL INFORMATION
Blue Bird heaters are hot water type which depend on heat generated by the engine for their function.
Heat from the engine is picked up by the engine coolant which is pumped through the heaters inside the
body and back into the engine. A typical heater inside the body is made of a heat exchanger coil and fans
which move air across the coil. Air moving across the coil picks up heat from the engine coolant and transfers
it into the body.
Satisfactory performance of the body heaters is basically dependent upon:
1. Adequate engine (coolant) temperature—this can be altered by thermostat rating (which should never
be higher than recommended by the engine manufacturer) and/or shutters.
2. Adequate coolant flow—this varies with engine speed and can be increased if necessary by the use of
an auxiliary water pump. The heaters are rated at six gallons per minute.
3. Proper fan operation—all motors have multiple speeds, and can most easily be checked for function
by operating the motor switches individually and listening for the speed variations.
Many other factors affect performance, but the three mentioned are most basic.
HEATER OPERATION
Be sure the engine radiator is full and all coolant flow valves are open. See charts on valve location. Do
not leave the engine running while opening or closing valves.
Warm up the engine to operating tempera-
ture with the engine at up to 1800 RPM, if possible, and turn on the heater fans and the auxiliary water pump
if so equipped.
Under extremely cold weather conditions, turning on the heater fans will cause the engine temperature to
drop noticeably as heat from the engine is being transferred into the body. But as air temperature inside the
body rises, engine temperature also rises. More heat will also be generated by the engine when it is caused to
work in moving the vehicle. This is especially noticeable with diesels which do not warm up at idle as readily
as gasoline engines. The fan speeds and subsequent air volumes can be controlled at the discretion of the
driver for defrosting and ultimate passenger comfort.
CONTROL PANEL
OUTLET LOCATIONS
The heater control panel is located in the center dash
panel, nearer the center of the bus body. The switches and
levers control the motors and air outlets as shown. (See
page 9.)
The main heater is located in the right front corner for-
ward of the entrance door and an auxiliary unit is located
under the driver’s seat. As indicated, the electrical switches
and mechanical levers control the volumes and directions
of air being moved. The main heater has a three-speed
control switch for manual low or high speed operation and
an additional maximum output position for flash defrost-
ing or the most extreme of conditions. All the air from the
main heater blower can be used for defrosting by leaving
the main outlet and foot warmer outlet closed.
CONTROL
PANEL
5
4
3
2
1
1. Driver’s Heater
2. Foot Warmer
3. Main
4. Defrost
5. Fresh Air
