Heaters; Heater Operation - Blue Bird D3RE 2014 Driver's Handbook Manual

HEATERS

Blue Bird heaters depend on engine generated heat to function. Heat from the en-
gine is picked up by the engine coolant, which is pumped through the heater cores
inside the bus, and then back into the engine. A typical heater inside the bus includes
a heat exchanger coil, (core) and fans which move air across the coil. Air moving
across the core picks up heat from the engine coolant and transfers it into the bus.
Satisfactory performance of the heaters is dependent upon:
• Adequate engine (coolant) temperature, which is controlled by the thermo-
stat rating (which should never be higher than recommended by the engine
manufacturer). Some All Americans feature optional shutters on the radiator
that help to regulate engine coolant temperature.
• Coolant flow, which varies with engine speed can be increased, if necessary,
with the use of an optional auxiliary water pump.
• Blower motors have multiple speeds and can be checked by operating the
motors individually, while listening for variations in speed.

Heater Operation

Be sure the engine radiator is full and all coolant flow valves are open. See charts on
valve location.
[CAUTION] Do not leave the engine running while opening or closing valves.
Warm the engine to operating temperature, running at up to 1,800 rpm if pos-
sible, and then turn on the heater fans and the auxiliary water pump if so equipped.
During extremely cold weather, operating the heater fans will cause the engine
temperature to drop noticeably as heat from the engine is transferred into the bus.
Also, the engine will generate more heat as it works under load. When the engine
reaches operating temperature, the driver can control heater blower speeds for opti-
mal defrosting and overall passenger comfort.
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DRIVER'S HANDBOOK