Troubleshooting
GUNE-SVX001A-EN
35
Failure to ignite.
Gas leak.
Shut off gas supply immediately!
Open all manual valves, check for leaks. Inspect all gas
piping and repair accordingly.
No power supply to the unit.
Turn on power supply, check fuses and replace if bad.
Thermostat not calling.
Turn up thermostat. Check for 24 V on terminals R and
W1 on terminal strip.
Defective high limit switch.
Check switch for continuity if open with no heat present;
replace.
Defective air pressure switch.
Check switch operation to ensure switch closes after
power vent purge period. If it does not make, check
tubing connections for blockage.
Defective spark ignitor, gas valve, thermostat or
transformer.
Check for continuity and voltage in safety and control
circuits; replace an item where continuity or voltage not
found.
Loose wiring.
Check all wiring per diagram.
Improper ground.
Check all ground wires and connections.
Improper thermostat or transformer wiring.
Check both for wiring according to diagram.
Condensation.
Improper venting.
Refer to
Unit under fired.
Check gas supply pressures to the unit. Refer to
.
Building/space too cold.
A minimum of 50°F (10°C) thermostat setting must be
maintained to deter formation of condensation. Refer to
Burners will not shut off.
Thermostat located improperly.
Relocate thermostat away from outside wall or drafts.
Improper thermostat wiring.
Check thermostat circuit for open and close on heater
terminal strip “R” and “W.”
Shorted circuit.
Check thermostat circuit for shorts or any staples
piercing wires.
Defective thermostat.
If thermostat is calling after set point has been satisfied,
replace.
Defective/sticking gas valve.
Check for 24 V on gas valve terminals when thermostat
not calling. Replace if necessary.
Defective control board.
Check for 24 V at terminals “R” and “W.” If not present
and board is not in flash code mode, replace board.
Excessive gas supply pressure.
Refer to
.
Rapid burner cycling.
Loose electrical connections at thermostat or gas valve. Tighten all electrical connections.
Unit cycling on high limit.
Check for proper air supply across heat exchanger and
proper gas supply.
Thermostat located improperly.
Relocate thermostat away from outside wall or drafts.
Defective high limit switch.
Jumper high limit switch wiring (orange and yellow
wires). If burner operating normally, replace switch.
Not enough heat.
Incorrect gas input.
Refer to
Unit undersized.
Is the unit output sized correctly for the heat loss of the
space? Has the space been enlarged? Is the unit located
in the space properly (refer to
)?
Thermostat malfunction.
Check thermostat circuit; 24 V on terminals “R” and “W”
on terminal strip.
Unit cycling on high limit.
Check air movement across the heat exchanger. Check
gas input to ensure unit is not over fired. Check heat
exchanger to ensure unit is not dirty.
Incorrect orifice sizes.
Check orifice size (refer to
Incorrect airflow.
See blower manufacturer for corrective action(s).
Table 14. Tubular duct furnace troubleshooting guide
Symptoms
Possible Cause(s)
Corrective Action