L.B. White 400 Tradesman Portable Forced Air - Manual (Page 14)

To replace the switch, remove the screws, spacers
and nuts holding the switch to the burner plate. See
Fig. 8 and 9..
FIG. 8
FIG. 9
TESTING
The switch should be tested annually.
1. Remove the switch assembly. Apply a small,soft flame
to the sensing disk of the switch. See Fig. 10. Be
careful not to melt the switch’s plastic housing when
conducting this test.
2. Within a short time, you should hear the contacts of
the switch opening.
3. Allow the switch to cool. The switch contacts will
close. Check for electrical continuity across the switch
terminals to ensure contacts have closed.
FIG. 10
AUTO RESET BACKFLASH SWITCH
14 13
1. Loosen the compression nut at the outlet of the
variable rate valve. See Fig.11
2. Remove both screws securing the valve bracket to
the heater panel.
3. Remove the valve assembly from the heater and
replace components as needed.
FIG. 11
VARIABLE RATE VALVE AND GAS CONTROL VALVE
SCREWS
SWITCH
SCREWS
COMPRESSION
NUT
VARIABLE RATE VALVE
GAS CONTROL VALVE
NUTS AND SPACERS