HVAC Troubleshooting Guides

HVAC troubleshooting guides: step-by-step checks for common problems that do not show an error code, grouped by equipment type.

Air Conditioner

• Not cooling All brands · Air Conditioner
• Amber STATUS or green COMM light not on Carrier · Air Conditioner
• Compressor will not run - winding and electrical checks - Carrier split systems Carrier · Air Conditioner
• Delay before the compressor restarts Carrier · Air Conditioner
• Hissing from the outdoor unit after it shuts off Carrier · Air Conditioner
• Outdoor unit unresponsive after several faults Carrier · Air Conditioner
• Superheat too high or too low on TXV system - Carrier split systems Carrier · Air Conditioner
• Two-stage unit not changing stages - Carrier 24ANB/25HNB/25HCB6 Carrier · Air Conditioner
• No cooling - R-32 GLXS/ALXS condenser Goodman · Air Conditioner
• Checking OAT and OCT thermistors - KeepRite C4A3/CXA6 KeepRite · Air Conditioner
• Low cooling capacity - check airflow and charge - Lennox EL16KC1 Lennox · Air Conditioner
• Outdoor unit will not start - Lennox EL16KC1 Lennox · Air Conditioner
• RDS leak-detected mode and start-up test - Lennox EL16KC1 Lennox · Air Conditioner
• Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Air Conditioner

Air Handler

• Blower not running - R-32 AMST/AWSF EEM air handler Goodman · Air Handler
• No electric heat - R-32 air handler heat kit Goodman · Air Handler
• Outdoor unit not communicating - ComfortBridge AVPTC/MBVC Goodman · Air Handler
• Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Air Handler
• Circulator pump does not run Rinnai · Air Handler
• Heat comes out in fan-only mode Rinnai · Air Handler
• Insufficient or no heat Rinnai · Air Handler
• Pump noisy at start-up Rinnai · Air Handler
• Reading and clearing fault history - Trane P0V0 modular blower Trane · Air Handler

Boiler

• No heat or some zones cold All brands · Boiler
• Annual service checklist - Navien NHB-H Navien · Boiler
• No space heat - Navien NHB-H / NFB-H Navien · Boiler
• Relief valve discharging - Navien NHB-H / NFB-H Navien · Boiler

Combi Boiler

• Hot water is cold or turns cold - Navien NCB-H Navien · Combi Boiler
• Hot water not hot enough or too hot - Navien NCB-H Navien · Combi Boiler
• No space heating - Navien NCB-H Navien · Combi Boiler
• No water from hot water tap - Navien NCB-H Navien · Combi Boiler

Gas Fireplace

• Flameworks millivolt valve: pilot outage or burner will not come on All brands · Gas Fireplace
• Maxitrol GV60 remote valve: fireplace will not light or respond All brands · Gas Fireplace
• Proflame (SIT DFC): fan, AUX outlet, split flow or OFF command not working All brands · Gas Fireplace
• Proflame (SIT DFC): pilot lights but main burner will not light or drops out All brands · Gas Fireplace
• Proflame (SIT DFC): pilot will not light or DFC locks out All brands · Gas Fireplace
• SIT 820 Nova millivolt valve: main burner will not come on or will not cycle All brands · Gas Fireplace
• SIT 820 Nova millivolt valve: pilot will not light All brands · Gas Fireplace
• SIT 820 Nova millivolt valve: pilot will not stay lit All brands · Gas Fireplace
• DSI fireplace: burner lights but will not stay lit Heat & Glo · Gas Fireplace
• DSI fireplace: ignitor sparks but burner will not light Heat & Glo · Gas Fireplace
• DSI fireplace: ignitor will not spark Heat & Glo · Gas Fireplace
• Fireplace with PVK-80 power vent: flames lifting or jumping Heat & Glo · Gas Fireplace
• HSI fireplace: flame comes on but will not stay lit Heat & Glo · Gas Fireplace
• HSI fireplace: hot surface ignitor will not glow Heat & Glo · Gas Fireplace
• HSI fireplace: ignitor glows but no flame Heat & Glo · Gas Fireplace
• Blower noisy, vibrating or rattling Napoleon · Gas Fireplace
• Carbon / soot buildup (service flowchart) Napoleon · Gas Fireplace
• Carbon / soot on glass, logs or firebox Napoleon · Gas Fireplace
• Complete unit shutdown - direct vent Napoleon · Gas Fireplace
• Complete unit shutdown - natural vent / vent-free Napoleon · Gas Fireplace
• Delayed ignition of main burner Napoleon · Gas Fireplace
• Exhaust fumes smelled in room / occupants get headaches Napoleon · Gas Fireplace
• Flames always too large or too small / carboning (over- or under-fired) Napoleon · Gas Fireplace
• Main burner flame is blue, lazy and transparent Napoleon · Gas Fireplace
• Main burner goes out and pilot goes out Napoleon · Gas Fireplace
• Main burner goes out during operation Napoleon · Gas Fireplace
• Main burner goes out; pilot stays on Napoleon · Gas Fireplace
• Main burner low flame Napoleon · Gas Fireplace
• Main burner will not light - direct vent / vent-free Napoleon · Gas Fireplace
• Main burner will not light - natural vent Napoleon · Gas Fireplace
• Odour from fireplace Napoleon · Gas Fireplace
• Oil-canning (popping/banging metal noise) Napoleon · Gas Fireplace
• Pilot drops out during operation - direct vent Napoleon · Gas Fireplace
• Pilot drops out during operation - natural vent Napoleon · Gas Fireplace
• Pilot drops out during operation - vent-free Napoleon · Gas Fireplace
• Pilot flame appearance diagnosis and adjustment Napoleon · Gas Fireplace
• Pilot goes out when the gas knob is released Napoleon · Gas Fireplace
• Pilot goes out while standing (main burner OFF) Napoleon · Gas Fireplace
• Pilot lit, no gas to main burner (knob on HI, switch/thermostat ON) Napoleon · Gas Fireplace
• Pilot will not light Napoleon · Gas Fireplace
• Pilot will not light (service flowchart) Napoleon · Gas Fireplace
• Pilot will not stay lit - direct vent Napoleon · Gas Fireplace
• Pilot will not stay lit - natural vent Napoleon · Gas Fireplace
• Pilot will not stay lit - vent-free Napoleon · Gas Fireplace
• Remote control: blank display or cannot turn fireplace off Napoleon · Gas Fireplace
• Remote control: pairing / code setting and multiple remotes Napoleon · Gas Fireplace
• Remote control: receiver will not turn fireplace on, shuts off by itself, or turns on unexpectedly Napoleon · Gas Fireplace
• Test: door gasket seal (paper test) Napoleon · Gas Fireplace
• Test: gas inlet and manifold pressure Napoleon · Gas Fireplace
• Test: gas valve magnet coil and operator coil Napoleon · Gas Fireplace
• Test: spill switch and wall switch/thermostat wiring Napoleon · Gas Fireplace
• Test: thermocouple and thermopile millivolts Napoleon · Gas Fireplace
• Venturi / air shutter adjustment Napoleon · Gas Fireplace
• Wall switch OFF but main burner comes on when gas knob turned ON Napoleon · Gas Fireplace
• White or grey film on glass, logs or firebox Napoleon · Gas Fireplace

Furnace

• Blowing cold air All brands · Furnace
• No heat All brands · Furnace
• Short cycling All brands · Furnace
• Burners will not light or stay lit - Carrier 58SB0A/58SB1A Carrier · Furnace
• Furnace not responding to thermostat - Carrier 58SB0A/58SB1A Carrier · Furnace
• Control display blank, furnace dead - Daikin DR96TN/DD96TN Daikin · Furnace
• Furnace not paired with R-32 cooling - disable A2L function - Daikin DR96TN/DD96TN Daikin · Furnace
• No heat - Daikin DR96TN/DD96TN Daikin · Furnace
• Control display blank, furnace dead - Goodman/Amana 9-speed ECM furnaces Goodman · Furnace
• No heat - Goodman/Amana 9-speed ECM furnaces Goodman · Furnace
• Poor combustion / flame problems - Goodman/Amana GM9C96 Goodman · Furnace
• Check inlet gas pressure ICP · Furnace
• Component self-test ICP · Furnace
• No heat - control does not respond to thermostat ICP · Furnace
• Reading and retrieving status codes ICP · Furnace
• No heat - SmartValve SV9501/SV9502 pilot does not light or main burner does not come on Johnson Controls · Furnace
• No heat, control ignores the thermostat - KeepRite (F/G)9MXE KeepRite · Furnace
• No heat, control ignores the thermostat - KeepRite (F/G)9MXT KeepRite · Furnace
• Reading stored codes and component test - KeepRite (F/G)9MXE KeepRite · Furnace
• Reading stored codes and component test - KeepRite (F/G)9MXT KeepRite · Furnace
• Blower motor does not run - Lennox SL280UHV ECM checks Lennox · Furnace
• Display shows two horizontal bars (soft disable) - Lennox SL297NV Lennox · Furnace
• Furnace will not run (no heat) - Lennox EL195UHNE Lennox · Furnace
• Furnace will not run (no heat) - Lennox SL297NV Lennox · Furnace
• Furnace will not run - Lennox SL280UHV checklist Lennox · Furnace
• Indoor blower does not run - Lennox EL195UHNE Lennox · Furnace
• Indoor blower does not run - Lennox ML180UHE Lennox · Furnace
• Poor ignition or combustion resonance - Lennox EL195UHNE Lennox · Furnace
• Poor ignition or loud combustion resonance - Lennox SL280UHNV Lennox · Furnace
• Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Furnace
• No light and no fan - furnace does not start Midea · Furnace
• Resetting a locked-out furnace Midea · Furnace
• Blower does not start after burners light Rheem · Furnace
• Burners go out before the heat call ends / short cycling Rheem · Furnace
• Communicating system not found / no communication Rheem · Furnace
• ECM blower does not start on heat Rheem · Furnace
• Furnace no heat - sequence troubleshooting Rheem · Furnace
• Furnace short cycles or does not hold setpoint Rheem · Furnace
• Gas valve does not shut off when heat call ends Rheem · Furnace
• Indoor blower does not start after burners light Rheem · Furnace
• Inducer (draft motor) does not start on heat call Rheem · Furnace
• Inducer does not run / does not run on low speed Rheem · Furnace
• Inducer runs 60 s then shuts off for 5 minutes, or runs continuously Rheem · Furnace
• Inducer runs 60 seconds then off for 5 minutes Rheem · Furnace
• No heat - inducer (IDM) does not start Rheem · Furnace
• No heat - POWER LED off Rheem · Furnace
• Read target airflow from the CFM LED Rheem · Furnace
• Thermostat does not hold room temperature Rheem · Furnace
• Reading and clearing fault history - Trane S-Series IFC Trane · Furnace

Heat Pump

• Amber STATUS or green COMM light not on Carrier · Heat Pump
• Delay before the compressor restarts Carrier · Heat Pump
• Heat pump will not defrost - HK32EA defrost board Carrier · Heat Pump
• Noisy compressor or loud defrost shift - Carrier split systems Carrier · Heat Pump
• Outdoor ECM fan not running - Carrier 25HNB9/24ANB1 Carrier · Heat Pump
• Outdoor unit unresponsive after several faults Carrier · Heat Pump
• Outdoor unit will not run - HK32EA defrost board heat pumps Carrier · Heat Pump
• No heat - R-32 GLZS/ALZS heat pump Goodman · Heat Pump
• Outdoor coil iced / no defrost - R-32 GLZS/ALZS heat pump Goodman · Heat Pump
• Reversing valve not shifting - ComfortNet heat pumps Goodman · Heat Pump
• Compressor will not run - Gree ductless Gree · Heat Pump
• Louver will not swing - Gree ductless Gree · Heat Pump
• Noise or vibration - Gree ductless Gree · Heat Pump
• Outdoor fan will not run - Gree ductless Gree · Heat Pump
• Unit will not start - Gree ductless Gree · Heat Pump
• Water leaking from indoor unit - Gree ductless Gree · Heat Pump
• Weak cooling or heating - Gree ductless Gree · Heat Pump
• Comfort Alert module basics ICP · Heat Pump
• Defrost not working - test the defrost board ICP · Heat Pump
• Forcing a defrost to test the board - KeepRite N4H4/R4H4/WCH4/NXH5 KeepRite · Heat Pump
• Outdoor unit will not run or will not defrost - KeepRite heat pump defrost board (FAST 1173636/1177927/1190281) KeepRite · Heat Pump
• Heat pump not defrosting / outdoor coil iced - Lennox EL16KP1 / ML14KP1 Lennox · Heat Pump
• Low capacity or abnormal pressures - Lennox EL16KP1 / ML14KP1 Lennox · Heat Pump
• Outdoor unit will not start - Lennox EL16KP1 / ML14KP1 Lennox · Heat Pump
• Two horizontal lines on display (soft disable) - Lennox communicating Lennox · Heat Pump
• Indoor board LED1 and LED2 both off - no power Mitsubishi · Heat Pump
• Indoor board LED2 blinking - remote controller line problem Mitsubishi · Heat Pump
• Indoor fan does not run Mitsubishi · Heat Pump
• PLEASE WAIT stays on, or an error shows about 2 minutes after power-up Mitsubishi · Heat Pump
• Heat pump will not defrost / incomplete or excessive defrost Rheem · Heat Pump
• Insufficient cooling / pressure problems Rheem · Heat Pump
• Outdoor fan runs but compressor does not Rheem · Heat Pump
• Outdoor unit will not run Rheem · Heat Pump
• Forcing a defrost - Trane 5TWR7 Trane · Heat Pump

Mini-Split

• Indoor unit leaking water All brands · Mini-Split

Tankless Water Heater

• No hot water All brands · Tankless Water Heater
• Water temperature fluctuates All brands · Tankless Water Heater
• Hot water slow to reach fixtures - Navien NPE-2 Navien · Tankless Water Heater
• Hot water turns cold - Navien NPE-2 Navien · Tankless Water Heater
• No water from hot tap - Navien NPE-2 Navien · Tankless Water Heater
• Water not hot enough or too hot - Navien NPE-2 Navien · Tankless Water Heater
• Cleaning ignition and flame rods - Noritz Noritz · Tankless Water Heater
• Cleaning the fan and burner - Noritz EZ/NRCR/CDV Noritz · Tankless Water Heater
• Descaling (flushing) the heat exchanger - Noritz Noritz · Tankless Water Heater
• Draining to prevent freezing - Noritz EZ/NRCR Noritz · Tankless Water Heater
• Field gas conversion NG to LP - Noritz NRCR/EZ Pro Noritz · Tankless Water Heater
• Heat exchanger replacement - Noritz NRC111 / NCC199 Noritz · Tankless Water Heater
• Heater does not fire when hot water is opened - Noritz tankless Noritz · Tankless Water Heater
• Recirculation not working or hot water slow - Noritz NRCR Noritz · Tankless Water Heater
• Water not hot enough or temperature fluctuates - Noritz tankless Noritz · Tankless Water Heater

Homeowner? Plain-language help: furnace not turning on, no hot water, AC not cooling