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SYMPTOMS
POSSIBLE CAUSE(S)
CORRECTIVE ACTION
A. Yellow tip flame (some
yellow tipping on LP
gas is permissible).
1. Clogged air inlet filter.
2. Clogged main burners.
3. Insufficient combustion air.
4. Possibly over fired.
1. Clean filter.
2. Clean mesh burner.
3. Insufficient combustion air.
4. Check CO
2
.
B. Floating flame.
1. Insufficient combustion air.
2. Air leak into combustion chamber or
inducer failure.
1. Clean combustion air inlet openings or filter.
2. Determine cause and repair accordingly.
C. Gas odor.
1. Shut off gas supply immediately!
2. Leaking port on valve.
3. Blocked heat exchanger.
4. Blocked flue collector.
5. Negative pressure in the building.
1. Inspect all gas piping and repair.
2. Check to ensure valve ports are seated.
3. Clean heat exchanger/flue.
4. Clean flue collector.
5. See INSTALLATION.
D. Delayed ignition.
1. Improper ground.
2. Bad or broken spark cable.
3. Faulty control.
4. Pressure regulator set too low.
5. Main burner and/or orifice dirty.
6. Improper venting.
1. Check grounding wires and spark bracket connections.
2. Inspect spark cable connections and cuts.
3. Check to ensure spark is energized after pre-purge period.
4. Test and reset manifold pressure refer to OPERATION.
5. Clean orifice or burners.
6. Refer to INSTALLATION.
E. Failure to ignite.
1. Gas supply is off.
2. No power supply to unit.
3. Thermostat not calling.
4. Defective high limit.
5. Defective drafter prove switch.
6. Loose wiring.
7. Improper ground.
8. Improper thermostat or transformer wiring.
9. Condensate trap clogged or leaking.
10. Defective ignition control.
11. Cap off pressure tubing
1. Open all manual valves “check for leaks”.
2. Turn on power supply, check fuses and replace if bad.
3. Turn up thermostat, Check for 24V on terminals R and W1
on terminal strip.
4. Check switch for continuity if open with no heat present,
replace.
5. Check switch operation to ensure switch closes after
drafter purge period. If it does not make/check tubing
connections/ blockage.
6. Check all wiring per diagram.
7. Check all ground wires and connections.
8. Check both, for wiring according to diagram; check for
24V at gas valve terminals during trial for ignition period if
present and valve does not open. Replace valve.
9. Clean condensate trap.
10. Replace ignition control
11. Re-install cap on tubing.
F. Burners will not shut off. 1. Thermostat located incorrectly.
2. Improper thermostat wiring.
3. Shorted circuit.
4. Defective sticking gas valve.
5. Excessive gas supply pressure.
1. Relocate thermostat away from outside wall or drafts.
2. Check thermostat circuit for open and close on terminal
strip on heater “R” and “W”.
3. Check thermostat circuit for shorts, staples piercing wires.
4. Check for 24V on gas valve terminals when thermostat is
not calling.
5. Refer to INSTALLATION.
G. Rapid burner cycling.
1. Loose electrical connections at thermostat
or gas valve.
2. Excessive thermostat heat anticipator
setting.
3. Unit cycling on high limit.
4. Poor thermostat location.
5. An improper ground.
1. Tighten all electrical connections.
2. Adjust heat anticipator setting for longer cycles. Refer to
ELECTRICAL CONNECTIONS.
3. Check for proper air supply across heat exchanger and
proper gas supply.
4. Relocate thermostat.
5. Refer to INSTALLATION.
H. Noisy power venter.
1. Power venter wheel loose.
2. Power venter wheel is dirty.
3. Power venter wheel is rubbing on the
housing.
1. Replace or tighten.
2. Clean power venter wheel.
3. Realign power venter wheel.
I. Fan will not run.
1. Loose electrical connections.
2. Defective motor or overload.
3. Defective control board.
4. Defective fan relay.
1. Check and tighten wires on fan circuit.
2. Test for 115V on terminal ACB Heat and “L2” if voltage is
present replace motor.
3. Test for 115V on terminal ACB Heat and “L2” on the control
board, if voltage is not present 45 seconds after trial for
ignition replace board.
4. Check for 24 volts on terminals 24 and 0. Check for 115V
on normally open relay contact when calling.
J. Fan motor turns on
and off while burner is
operating.
1. Motor overload protection is tripping.
2. Loose wiring or connection.
3. Control board is defective.
1. Check motor amps against motor name plate, check
voltage, replace if found defective.
2. Check for 115V between motor leads.
3. Check terminal 24 and 0 for 24 volts. If voltage is not
constant, replace control board.
HIGH EFFICIENCY GAS-FIRED UNIT HEATER TROUBLESHOOTING GUIDE
