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SERVICE
Possible Cause
1. Check the gas pressure reading on the gauge. Problem
may be due to insufficient gas regulator setting. Tempo-
rarily decrease the hi-lo fire thermostat setting to verify
that the thermostat will function and cause the burner to
cycle. If burner will cycle at the reduced thermostat
setting, it indicates that the problem was due to insuffi-
cient heat to satisfy the original setting. Increase the
gas regulator setting for additional heat output. Do not
exceed the maximum pressure listed in this manual.
2. Hi-lo fire thermostat control may be defective. If the
burner still will not cycle to lo-fire after decreasing the
thermostat, the problem may be due to a broken or
kinked thermostat sensor tube. Observe reading on the
thermometer. Replace control assembly if it cannot be
set to cause its switch to go to the open circuit position
with normally hot air plenum temperatures.
3. If the burner continues to operate on hi-fire, check the
hi-fire gas solenoid valve for a stuck or blocked open
condition, or for reversed gas pipe connections. The
solenoid valve must not allow gas flow when its coil is
not energized.
1. Check for an excessive lo-fire gas pressure setting.
Observe pressure setting shown on gauge, and
compare reading with recommended low pressure
settings listed in this manual. Readjust lo-fire setting on
flow control valve, if necessary.
2. Check for improperly adjusted or defective hi-lo fire
thermostat control. Temporarily increase the tempera-
ture setting. If the heater will still not cycle, check for
problem in the control wire connections. The control
wires should be connected to terminals R and B of the
thermostat, so the switch will open upon temperature
rise. If the burner will cycle with these two wires
connected together, the thermostat is faulty.
3. Check for improperly connected or faulty hi-fire gas
vapor solenoid valve. Correct any poor connections or
defective wiring. If wiring appears proper, problem may
be caused by a burned out valve coil or defective valve.
Replace hi-fire solenoid valve, or its coil, if defective.
Problem
Burner operates-But will not cycle from hi-fire to lo-fire.
Burner operates-But will not cycle from lo-fire to hi-fire.