Ignition Transformer; Fuel Solenoid Valve; Fan Switch - Desa B350D Service Manual

H I G H P R E S S U R E P O R T A B L E F O R C E D A I R H E A T E R S E R V I C E M A N U A L

Ignition Transformer

The ignition transformer operates on 120V/
60Hz. It delivers approximately 5,000 volts to
the spark plug. The spark plug ignites the fuel
sprayed from the nozzle assembly. The igni-
tion transformer operates continuously while
the heater is running.
The ignition transformer has no internal ser-
vice parts. Replace the ignition transformer if
defective.
Transformer has high voltage output.
Always unplug heater before replacing
transformer. Use extreme caution when
testing transformer. Severe electrical
shock can occur.

Fuel Solenoid Valve

The solenoid valve is an electro-magnetic
device. It is mounted directly behind the
burner head body. The solenoid valve acts
as an on/off valve for fuel flow to the nozzle.
When the thermostat on the heater turns
heater on, the solenoid valve opens, allow-
ing fuel to flow to the nozzle. When the
thermostat on the heater turns heater off, the
solenoid valve closes, preventing fuel from
reaching the nozzle.

Fan Switch

The fan switch is a two-position, tempera-
ture-activated, bi-metal switch. The switch
allows the motor to continue turning fan after
thermostat shuts off heater. This helps cool
the combustion chamber.
When the heater is first turned on, power to
the motor is routed thru the thermostat,
flame control, and the normally closed con-
tacts one and three of the fan switch. After a
few minutes of operation, the temperature of
the combustion chamber increases. This
causes the bi-metal material within the fan
switch to warp and close contacts one and
two and open contacts one and three. Power
to the motor is then routed thru contacts one
!
WARNING
WARNING ICON G 001
Figure 8 - Ignition Transformer
Figure 9 - Fuel Solenoid Valve
and two, bypassing the flame control and the
thermostat. This switch allows the motor
and fan to continue to run. When the cham-
ber cools enough to allow the fan switch to
close contacts one and three, the motor will
shut off.
Figure 10 - Fan Switch
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