My indoor temperature reading is not working - Heating & Cooling

Have you changed the batteries in the outdoor temperature sensor?

The indoor temperature and humidity and outdoor temperature readings can be calibrated on the display to improve accuracy. Calibration can improve accuracy when sensor placement or environmental factors impact your data accuracy. 1. To access calibration mode, press AND HOLD the "?", "?", and "SET" buttons for at least 5 seconds. 2. Once in calibration mode, the preference you are currently setting will be highlighted on the display. 3. Press the "?" or "?" buttons to calibrate the data value higher or lower from the actual reading. 4. Press the "SET" button to confirm the calibration adjustment. The " " icon will remain illuminated next to calibrated values. 5. The next adjustable data will begin flashing, indicating it is ready to be calibrated. Repeat Steps 1 - 4 to calibrate additional data. The preference set order is as follows: OUTDOOR TEMPERATURE INDOOR TEMPERATURE INDOOR HUMIDITY BAROMETRIC PRESSURE (must be set to MANUAL mode; see page 12) After 20 seconds of inactivity, the display will save the adjustments and exit calibration mode. Note: Calibrations will be erased if the display is reset or if batteries are removed and the power adapter is unplugged.

If there are no active failures or lockouts, the display will show a double dash, "- -". If there is a code listed, see the unit "Diagnostic Codes" chart for a list of definitions. Error Codes Problem FP Freeze Protection Engaged. The room temperature measured by the wireless remote thermostat or indoor ambient thermistor active sensor falls below 40°F. No Action required. This setting will disengage when the room temperature rises above 43°F. Fd Front Desk switch is closed. All outputs are switched off. Open front desk switch to allow occupant unit operation. Eo Un-Configured Service Board - All operation held awaiting configuration. Enter Configuration Menu and set "C3" to "C" for coolers with electric heat or "H" for heat pumps. EH Emergency Hydronic Engaged. The EHH switch is closed. Compressor is switched off. Open front emergency hydronic switch to allow occupant unit operation. LS Load Shedding Engaged. The LS switch is closed. Compressor and Electric heat is switched off. Open load shedding switch to allow occupant unit operation. On Control is configured to respond to a wired thermostat. No action if a wired thermostat is being used. Otherwise, see Configuration Settings. oP Open Door Lockout (DS1 & DS2 open; wireless). Close Room Door. Unit will not condition space with door open. nP Window Switch Lockout - (LS & INN open). Close Room Door or Window. Unit will not condition space with door or window open. HP Heat Sentinel - (WIAT > u3). No action required. This setting will disengage when the room temperature falls. Ur Un-Rented Status (EHH & INN or wireless). Front Desk needs to set to Rented mode (if applicable). F1 Indoor Ambient Thermistor reads outside the range -20°F to 200°F & the wireless thermostat is not communicating to the unit control or Indoor Ambient Thermistor (IAT) without a wireless remote thermostat reads outside the range -20°F to 200°F. Replace black Indoor Ambient Thermistor or Wireless Remote Thermostat. F2 Wireless Remote Thermostat failure. Replace Wireless Thermostat. F3 Indoor Ambient Thermistor reads outside the range -20°F to 200°F. Replace black Indoor Ambient Thermistor. F4 Indoor Coil Thermistor either above or below operating tolerances. Replace Red Indoor Coil Thermistor. F5 Wireless Thermostat failure. Attempt to rebind Wireless Thermostat or Replace Wireless Thermostat. F6 Indoor Discharge Thermistor either above or below operating tolerances. Replace Yellow Indoor Discharge Thermistor. Fb Low Remote Battery Warning. Replace Batteries in Wireless Devices. H1 High Voltage Protection engaged. Power supply voltage is to high. Check for incoming power at correct voltage. br Brown Out Protection engaged. Power was lost or voltage is low. Check for incoming power at correct voltage. L6 Discharge Air Too Hot. Clean Filter or Remove Air Blockage. LC Outdoor Coil Thermistor temperature high. Clean Condenser Coils, Check Fan for fault. Code will reset after cleaning. C2 Indoor Air Recirculation. Large delta between thermostat and return. Clean Filter or Remove Air Blockage or Close Vent Door or Improve indoor to outdoor seal. C5 Outdoor Coil temperature too high for outdoor ambient temperature. Check for Blocked Outdoor Air or Clean Coil. C1 Indoor Coil is freezing up. Clean filter, Check for fan and blower operation, Check for Refrigerant loss or Restricted capillary tube. C3 Indoor Coil is freezing up. Clean filter, Check for fan and blower operation, Check for Refrigerant loss or Restricted capillary tube. C4 Indoor Coil froze up. Clean filter, Check for fan and blower operation, Check for Refrigerant loss or Restricted capillary tube. C6 Poor Unit Performance. Check for blower motor, compressor, or electric heat operation. C7 Indoor Freezing Lockout (ICT - IAT > 20) +10 Min. Clean filter, Check for fan and blower operation, Check for Refrigerant loss or Restricted capillary tube.

Most air cons now have temperature sensors all over the machine. When it reaches temp on heat cycle, the machine usually shuts down both indoor and outdoor units but the indoor unit will keep running for a few minutes with the fan on only to cool the indoor unit down. This prevents the unit reading the wrong temperature. It stops the sensor(s) reading the heat from the indoor unit rather than the heat in the air in the room.

Is yours the colour screen one? I thought I was getting the same readings from both units no matter where I put them, but I put a bag of peas on top of one unit and the temperature and humidity dropped massively so mine seems to be working, even if it didn't seem to be working to begin with. Weird unit, why the two sensors anyway, I dont get it.

Did you reset the sensors after replacing the batteries? Bring the sensor inside and close to the main unit. Replace batteries on both units. Use a thumb tack and stick it into small reset hole near battery compartment to reset both units. If that doesn't work, your sensor needs more troubleshooting or needs to be replaced.

dear sir/madam i think.... mr Slim A control R407c & R410a systems.
P6 = indoor coil frost protection in cooling or indoor coil overheat protection in heating.

Cooling
One of the 2 indoor coil sensors reads minus 15 deg C for 3 mins.
Heating
One of the indoor coil sensors reads over 70 deg C.

If you are sure the refrigerant charge is correct & system operation is correct then it could be a coil temperature sensor reading wrong temperature.
If you have one of those little monitor things which plug into the outdoor circuit board you can monitor the indoor coil temperature.
On later type remote controllers you can get all operating data like temp sensor data but you will need a service manual to do this.
Or you can measure the ohms resistance of the temp sensors & compare with the chart in the service manual. if you can do it by yourself do if not then contatct ot mitsubishi maintenance personnnel for furhter action, thank you hope answer the question please vote!

Where are you measuring the indoor temperature?
To compare it to the thermostat temperature you have to measure both temperatures at thermostat.
The thermostat will only control the temperature at the thermostat, not any where else in the room.
The room temperature depending on insulation in walls and ceiling and distance from outside wall and outside temperature, can be as high as 10° difference from outside wall to inside wall of house.
The lower the outside temperature, the greater the room difference in heating. The higher the outside temperature the greater the room difference in cooling.