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PROBLEM
BLOWER RUNS
CONTINUOUSLY
HOT SURFACE IGNITER
NOT GLOWING
FOLLOWING WARM-UP
PERIOD
VENT PIPE TOO HOT
331432-00
POSSIBLE CAUSE(S)
1. Air pressure switch not closing due to
insuffi cient draft – check for:
a. Vent piping blocked
b. Piping length too long
c. Clogged/dirty blower
2. Disconnected, torn or blocked pressure
switch hose from air pressure switch to
blower housing
3. Defective pressure switch
4. High limit switch open due to excessive
vent temperature or defective switch
1. 120VAC polarity reversed at 120VAC
outlet receptacle
2. Defective hot surface igniter
3. Defective gas control valve/thermostat
1. Blower high limit switch fails to open -
switch defective
2. Not enough dilution air to mix with fl ue
gases
3. Air in room too hot for mixing with fl ue
gases
4. Wrong burner orifi ce
CORRECTIVE ACTION
1. Determine cause of insuffi cient draft.
Check draft with manometer at pressure
switch
a. Remove blockage
b. Reduce vent length/increase vent
size
c. Clean blower wheel
2. Reconnect or replace pressure switch
hose
3. Replace defective pressure switch
4. Determine cause of overheating check
for: overfi ring, insuffi cient air supply, high
ambient air temperature
1. Reverse polarity at 120VAC outlet
receptacle
2. Replace igniter
3. Replace gas control valve/thermostat
1. Replace blower high limit switch
2. Proper air circulation must be provided
for combustion and dilution of fl ue temp
3. Increase ventilation to lower room
temperature
4. Install correct orifi ce.
47
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