Carrier error codes
37 documented codes with ranked causes, repair costs, and step-by-step guidance.
Carrier heat pump code chart (6) Carrier furnace code chart (30)
Carrier Heat Pump — Ice on outdoor unit Carrier Heat Pump Ice on Outdoor Unit: Causes & Fixes Ice on your Carrier heat pump outdoor unit? Learn normal frost vs. problem ice, the main causes, safe checks, and repair costs from $0 to $2,500+. Carrier Heat Pump — Stuck in defrost mode Carrier Heat Pump Stuck in Defrost Mode: Causes & Fixes Carrier heat pump stuck in defrost? Learn the causes (defrost board, sensor, reversing valve, relay), safe checks, and repair costs from $0 to $1,800+. Carrier Heat Pump — Frozen and not defrosting Carrier Heat Pump Frozen and Not Defrosting: Causes & Fixes Carrier heat pump iced over and not defrosting? Learn the causes (airflow, runoff, defrost sensor, board, low charge), safe fixes and repair costs. Carrier Heat Pump — Not cooling Carrier Heat Pump Not Cooling: Causes, Fixes & Costs Carrier heat pump not cooling? Learn the causes, from a stuck reversing valve to low refrigerant, which fixes are safe, and what repairs cost. Carrier Heat Pump — Auxiliary heat on constantly Carrier Heat Pump Aux Heat On Constantly: Causes & Fixes Carrier heat pump running on aux heat nonstop? Learn the causes, from thermostat setup to defrost and refrigerant faults, plus safe fixes and repair costs. Carrier Heat Pump — Not heating Carrier Heat Pump Not Heating: Causes, Fixes & Costs Carrier heat pump not heating? Learn the likely causes (thermostat, defrost, reversing valve, refrigerant, compressor), safe fixes, and US repair costs. Carrier Furnace — Pressure switch stuck open Carrier Furnace Pressure Switch Stuck Open: Causes & Fixes Carrier furnace pressure switch stuck open: blocked vent, weak inducer or condensate clog causes plus fixes and repair costs ($0 DIY–$1,200). Carrier Furnace — Runs constantly but not enough heat Carrier Furnace Runs Constantly But Not Enough Heat Carrier furnace runs nonstop but the house stays cold. Causes from dirty filters to failing heat exchangers, plus DIY checks, fixes and repair costs. Carrier Furnace — Won't ignite Carrier Furnace Won't Ignite: Causes, Fixes & Costs Carrier furnace won't ignite? Common causes include a dirty flame sensor, bad igniter, gas or pressure switch faults, plus DIY checks and repair costs. Carrier Furnace — Won't turn on Carrier Furnace Won't Turn On: Causes, Fixes & Costs Carrier furnace won't turn on? Common causes include a tripped breaker, dead thermostat batteries, blown fuse or bad door switch. Fixes and costs inside. Carrier Furnace — Blower not running Carrier Furnace Blower Not Running: Causes & Fixes Carrier furnace blower not running? Causes from bad capacitors to door switches, plus fixes and repair costs from $0 DIY to $1,200. Carrier Furnace — Blower won't shut off Carrier Furnace Blower Won't Shut Off: Causes & Fixes Carrier furnace blower running non-stop? Causes include fan setting, bad limit switch, or a stuck fan relay, plus DIY checks and repair costs. Carrier Furnace — Blowing cold air Carrier Furnace Blowing Cold Air: Causes & Fixes Carrier furnace blowing cold air? Common causes are thermostat fan settings, ignition faults, overheating and flame-sensor issues, plus fixes and costs. Carrier Furnace — Clicking but not starting Carrier Furnace Clicking But Not Starting: Causes & Fixes Carrier furnace clicking but not starting? Causes include a cracked igniter, dirty flame sensor, or weak inducer draft. Fixes and costs from $0 to $1,200. Carrier Furnace — Flame sensor problems Carrier Furnace Flame Sensor Problems: Causes & Fixes Carrier furnace flame sensor problems cause short cycling and no heat. Learn the causes, safe checks and repair costs ($0 DIY reset to $1,200 pro). Carrier Furnace — Ignition lockout Carrier Furnace Ignition Lockout: Causes, Fixes & Costs Carrier furnace ignition lockout means failed ignition after repeated tries. See causes, safe checks, fixes and repair costs from $0 DIY to $1,200. Carrier Furnace — Leaking water Carrier Furnace Leaking Water: Causes, Fixes & Costs Carrier furnace leaking water? Causes include clogged condensate lines, bad drains, and flue issues, plus fixes and repair costs from $0 to $3,000+. Carrier Furnace — Loud bang on startup Carrier Furnace Loud Bang on Startup: Causes & Fixes Carrier furnace loud bang on startup usually means delayed ignition or duct oil-canning. Learn causes, safe checks, fixes and repair costs. Carrier Furnace — Short cycling Carrier Furnace Short Cycling: Causes, Fixes & Costs Carrier furnace short cycling? Learn the top causes—dirty filter, overheating, flame sensor, oversizing—plus safe checks, fixes and repair costs. Carrier Furnace — Keeps shutting off Carrier Furnace Keeps Shutting Off: Causes, Fixes & Costs Carrier furnace keeps shutting off? Causes include dirty filters, flame sensor, limit switch and pressure switch faults, plus fixes and US repair costs. Carrier Furnace — Code 12 Carrier Furnace Code 12: Meaning, Causes & Fixes Carrier Furnace Code 12 means power was interrupted during heating. Causes, safe checks, fixes and repair costs for US homeowners. Carrier Furnace — Code 21 Carrier Furnace Code 21: Gas Valve Relay Fault & Fixes Carrier Furnace Code 21 means a gas heating lockout from a shorted valve relay or mis-wired gas valve. Causes, fixes and pro repair costs inside. Carrier Furnace — Code 23 Carrier Furnace Code 23: Pressure Switch Did Not Open Carrier Furnace Code 23 means the pressure switch stayed closed before the inducer started. Causes, safe checks, fixes & repair costs. Carrier Furnace — Code 24 Carrier Furnace Code 24: Blown Secondary Fuse & Fixes Carrier Furnace Code 24 means the 3A low-voltage fuse is blown from a 24V wiring short. Causes, fixes, and repair costs for US homeowners.