Not heating: Codes, Causes & Fixes
When a dishwasher, washer, dryer or oven runs but doesn't heat, the usual suspects are the heating element, the temperature sensor (thermistor) that controls it, a safety thermal fuse or – in dryers – restricted airflow that trips the overheat protection. Error codes often distinguish between a sensor fault and a heater circuit fault, which helps decide what to test. Heating elements run on mains voltage, so replacement is a job for a technician unless you are qualified; for boilers see “No heat or hot water”.
71Codes
3.0Average severity
17%High or critical
41%DIY-friendly
Severity distribution
Most viewed
U4
Daikin · Air Conditioner / Heat Pump
The indoor unit has lost its data link with the outdoor unit, so the system can't cool or heat.
Moderate
E6
Mitsubishi Electric · Air Conditioner / Heat Pump
The indoor unit isn't getting valid signals back from the outdoor unit over the S3 wire.
Moderate
D80
LG · Dryer
LG Flow Sense detected restricted airflow in the vent. The dryer still runs, but lint buildup…
Moderate
HE
Samsung · Dryer
The Samsung dryer isn’t heating as expected – often no heat at all. Check power, gas supply…
Moderate
F2
GE Appliances · Oven / Range
The control saw the oven running hotter than its safety limit and shut the heat off.
High
F3
Whirlpool · Oven / Range
The control can't get a valid reading from the oven temperature sensor, so it won't heat…
Moderate
All codes (12)
13
Carrier · Air Conditioner / Heat Pump
A limit or rollout switch stayed open too long, so the furnace has locked itself out for 3…
High
C-21
Samsung · Oven / Range
The Samsung range sensed too high an oven temperature – real overheating or a bad sensor…
High
CH21
LG · Air Conditioner / Heat Pump
CH21: the outdoor inverter's power module saw a dangerous current peak and cut power…
High
CH38
LG · Air Conditioner / Heat Pump
LG's protection stopped the system because the refrigerant level or pressure looks too low.
High
d90
LG · Dryer
LG's duct sensor found a severe exhaust restriction (about 90%). Clean the whole vent before…
High
d95
LG · Dryer
d95 is LG's highest duct-blockage level: about 95% restricted. Don't run more loads until…
Critical
E110
Navien · Water Heater / Boiler
The fan can't move enough air through the vent system – most often a clogged intake filter…
High
F2
GE Appliances · Oven / Range
The control saw the oven running hotter than its safety limit and shut the heat off.
High
L5
Daikin · Air Conditioner / Heat Pump
L5: the outdoor inverter saw a current spike on the compressor output and shut the compressor…
High
P4
Midea · Air Conditioner / Heat Pump
P4 (PC 04 on newer displays): the outdoor board couldn't drive the inverter compressor…
High
U0
Daikin · Air Conditioner / Heat Pump
The outdoor unit has judged the system to be low on refrigerant and stopped the compressor…
High
U6
Mitsubishi Electric · Air Conditioner / Heat Pump
The outdoor inverter saw too much compressor current and shut down to protect the power module.
High