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 (71)
P1
MRCOOL · Air Conditioner / Heat Pump
The outdoor unit saw supply voltage too high or too low and stopped the compressor to protect…
Moderate
P1
Mitsubishi Electric · Air Conditioner / Heat Pump
P1: the indoor unit's return-air thermistor reads open or shorted, so the unit can't tell room…
Low
P4
Midea · Air Conditioner / Heat Pump
P4 (PC 04 on newer displays): the outdoor board couldn't drive the inverter compressor…
High
P6
Mitsubishi Electric · Air Conditioner / Heat Pump
P6: the indoor coil got too cold in cooling or too hot in heating – almost always an airflow…
Low
P8
Mitsubishi Electric · Air Conditioner / Heat Pump
The indoor coil isn't getting colder (or warmer) than the room after the compressor starts, so…
Moderate
tE
LG · Washing Machine
LG can't read the water temperature correctly or the water isn't warming. The thermistor…
Low
tE
Samsung · Dryer
The Samsung dryer can't trust its temperature reading. Clean the lint screen and vent, then…
Moderate
tE1
LG · Dryer
The LG dryer's thermistor circuit is reading open or out of range, so the control shuts off…
Moderate
U0
Daikin · Air Conditioner / Heat Pump
The outdoor unit has judged the system to be low on refrigerant and stopped the compressor…
High
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
U6
Mitsubishi Electric · Air Conditioner / Heat Pump
The outdoor inverter saw too much compressor current and shut down to protect the power module.
High