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Table 10—Troubleshooting Chart Con’t--Gas Furnace Operation
SYMPTOM
CAUSE
REMEDY
Water in gas line
Drain. Install drip leg.
No power to unit
Check power supply fuses, wiring or circuit
breaker.
No 24--v power supply to control circuit
Check transformer.
NOTE: Some transformers have internal over--
current protection that requires a cool--down peri-
od to reset.
Burners will not ignite
Mis--wired or loose connections
Check all wiring and wire nut connections
Burners will not ignite
Misaligned spark electrodes
Check flame ignition and sense electrode posi-
tioning.
Adjust as necessary.
No gas at main burners
1. Check gas line for air. Purge as necessary.
NOTE: After purging gas line of air, wait at least 5
minutes for any gas to dissipate before attempt-
ing to light unit.
2. Check gas valve.
Inducer pressure switch not closing
1. Check pressure switch wires, connections,
and tubing. Repair or replace if necessary.
Dirty air filter
Clean or replace filter as necessary
Gas input to unit too low
Check gas pressure at manifold match with that
on unit nameplate
Inadequate heating
Unit undersized for application
Replace with proper unit or add additional unit
Inadequate heating
Restricted airflow
Clean or replace filter. Remove any restriction.
Limit switch cycles main burners
Check rotation of blower, temperature rise of unit.
Adjust as necessary.
Poor flame characteristics
Incomplete combustion results in: Aldehyde odors,
carbon monoxide, sooting flame, floating flame
1. Tighten all screws around burner compartment
2. Cracked heat exchanger. Replace.
3. Unit over--fired. Reduce input (change orifices
or adjust gas line or manifold pressure).
4. Check burner alignment.
5. Inspect heat exchanger for blockage. Clean
as necessary.
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