Carrier furnace troubleshooting

ProblemCause Solution
Spark shorting out to main burnerCheck for loose or broken wiring at and between electronic con- trol box and electrode Replace wire as necessary
Check fuse or circuit breaker for 115-volt supply to furnace
Check 24-volt input to electronic control box If you read 24 volts and above steps have been completed, replace electronic control box assembly
Realign electrode tip away from main burner but maintain spark gap to pilot burner as noted above
No gas at pilot burnerCheck to see if pilot valve is opening Look for loose or broken wiring connections If no deficiency is found, replace valve assembly
Burners will not igniteNo 115-volt power to furnace No 24-volt power to control circuit Miswired or loose connections No gas at main burners
Flame probe or connecting lead is shorted or open
Dirty pilot — yellow flame
Connect to power supply Check fuse, wiring, or circuit breaker.
Check transformer — replace
Check all wiring and wirenut connections
Check to see if main valve is opening Look for loose or broken wiring connections If no deficiency is found, replace valve assembly
Correct electrical shorting or open circuit Clean pilot orifice
Inadequate heatingFurnace undersized for application Gas input to furnace too low
Limit switch cycles main burners
Replace with proper size furnace
Check gas pressure at manifold Clock gas meter for input If too low, increase manifold pressure, or replace with correct orifices
OFF setting of fan control set too high — reset
Dirty air filters — clean and reinstall
Blower speed too low — use faster speed top
Registers closed, restricted ductwork — open or remove restriction
Check heat anticipator setting on thermostat — readjust
Aldehyde odors, (CO), sooting flame — floating flameIncomplete combustion — poor flame characteristicsAir shutter on burners — closed — adjust to soft blue flame
Check all screws around flue outlets and burner compartment — tighten
LACK OF COMBUSTION AIR — see instructions Cracked heat exchanger — replace Overfired furnace — reduce input, or change orifices Check vent for restriction — clean as required

Error codes and troubleshooting