L.B. White 100 Tradesman Portable Forced Air - Manual (Page 15)

Test the ignitor periodically. With the gas supply shut
off, turn the heater on. If there is not a spark, or a
weak spark is evident, either check the gap of the
igniter electrode or clean the electrode.
--- Ensure the tip of igniter tip is 3.6 mm. from the
burner plate. See Fig.9.
--- To promote a strong spark and good flame sense,
periodically clean the igniter of dirt buildup using a
small wire brush or emery cloth.
FIG. 9
IGNITER
IGNITER
BURNER PLATE
1/8
14
BACKFLASH SWITCH
HEAT CHAMBER
BURNER PLATE
BACKFLASH SWITCH
SCREW
1/4
1. Remove the mounting screw from the switch’s
support bracket.
2. The replacement switch ships attached to its
mounting bracket. Ensure gap of switch to burner
plate is 1/4 inch.
FIG. 10
Testing the Backflash Switch
The switch is an auto reset temperature switch. It should be
tested at least once a year, normally when the heater is
given a thorough cleaning.
a. Remove the switch with bracket from the heater.
b. Holding the switch by its mounting bracket, apply a
soft flame only to the sensing portion on the backside
of the switch. Be careful not to melt the switch
housing when testing.
c. Within a short time you should here a pop coming
from the switch, indicating that the electrical contacts
have opened. Check the switch contacts for
continuity to verify the circuit has opened.
d. Allow the switch to cool down. The switch will reset
itself shortly. Check for continuity across the terminal
to verify contact closure.
FIG. 12
FLAME
SENSING SURFACE
BACKFLASH SWITCH
3.6 mm (.142”)