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Table 10 – Troubleshooting Chart -- Gas Furnace Operation
SYMPTOM CAUSE REMEDY
Burners will not ignite
Water in gas line Drain. Install drip leg.
No power to unit
Check power supply fuses, wiring o r circuit
breaker.
No 24--v power supply to control circuit
Check transfor mer.
NOTE: Some transformers have internal over--
current protection that requires a cool--down peri-
od to reset.
Mis--wired or l oose connections Check all wiring and wire nut connections
Misaligned spark el ectrodes
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 repl ace if necessary.
Inadequate heating
Dirt y air filter Clean or replace filter as necessary
Gas input to unit t oo low
Check gas pressure at manifold match with that
on unit nameplate
Unit undersized for application Replace with proper unit o r add additional unit
Restricted airflow Clean or replace filter. Remove any restriction.
Limit switch cycles main burners
Check rotation of blower, temperature ri se of unit.
Adjust as necessary.
Poor flame characteristics
Incomplete combustion results in: A ldehyde odors,
carbon monoxide, sooting flame, floati ng flame
1. Tighten all screws around burner compartment
2. Cracked heat exchanger. R eplace.
3. Unit over--fired. Reduce input (change orifices
or adjust gas line or manifold pressure).
4. Check burner alignment.
5. Inspect heat exc hanger for blockage. Clean
as necessary.
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