conjunction with a multiple element resistor, provides
the circuitry to make these motor selections possible.
17-20. Auxiliary Heaters.
a. Engine Compartment Heaters. The engine
compartment, particularly in vehicles equipped for arctic
operation, contain one or more auxiliary heating devices.
The most common devices are:
(1) Water Jacket Heater. The water jacket heater
Is an electric resistance-type heater that operates usually
from an external 110-volt power supply. The heating unit
usually Is installed in place of one of the cylinder block
core hole plugs.
(2) Engine Oil Heater. The engine oil heater Is
also an electric reslstance-type heater that operates from
an external 110-volt power supply. The engine oil heater
Is a bayonet-type device that fits In the engine in place of
Figure 17-30. Typical Heater Core
Blanket Heaters. Engine compartment
components also can be heated by blanket-type electric
f. Blower Motor. The blower motor Is a simple
heaters. These devices are used to heat the battery or
electric motor that drives a circular fan. This circular fan
can be used to cover the engine, retarding engine cool
commonly Is referred to as a squirrel cage. The controls
of the blower usually Include a three- or four-position
switch providing various speed choices to the operator.
The switch, In
Figure 17-31. Cable-Operated Mode Doors