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TABLE 11—TROUBLESHOOTING — HEATING
SYMPTOM CAUSE REMEDY
Burners will not ignite.
Water in gas line Drain. Install drip leg.
No power to furnace Check power supply fuses, wiring, or circuit breaker.
Miswired or loose connections Check all wiring and wirenut connections.
Burned-out heat anticipator in thermostat Replace thermostat.
Broken thermostat wire Run continuity check. Replace wire if necessary.
Misaligned spark electrodes
Check flame ignition and sense electrode positioning.
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 attempting to light unit.
2. Check gas valve.
Inadequate heating.
Dirty air filter Clean or replace filter as necessary.
Gas input to furnace too low
check gas pressure at manifold. Match with that on unit
nameplate.
Unit undersized for application Replace with proper unit or add additional unit.
Restricted airflow Clean or replace filter. Remove any restriction.
Blower speed too low
Use faster speed tap if available, or install alternate
motor.
Limit switch cycles main burners
Check rotation of blower, thermostat heat anticipator
settings, and temperature rise of unit. Adjust as neces-
sary.
Poor flame. characteristics
Incomplete combustion results in: Aldehyde odors, car-
bon monoxide, sooting flame, floating flame
1. Tighten all screws around burner compartments.
2. Cracked heat exchanger. Replace
3. Unit overfired. Reduce input (change orifices or ad-
just gas line or manifold pressure).
4. Check burner alignment.
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