Sensor check of daikin Unit

Good day all,

Ive recentley been working on a diakin ducted ac which has a UF fault.
Model FDYQ160KAV1 / RZQ160KV4A.

On this model , according to the service manual, the UF fault can be generated by the indoor coil sensor reading 14 degrees or more higher than the pressure transducer saturated suction pressure. This could indicate blockage , short of refrigerant etc....

R2T - Te > 14 C.

I have proven the pressure transducer to be ok and that the coil temp is running cold (5 C)

If i however read the sensor off the indoor contoller (02) It shows that sensor to be 20 C ( which brings up the UF fault after 20 min). The obvious conclusion is a faulty sensor. i removed the sensor and tested it in a glass of ice water and it seemed to react correctley over a range of temps.

My question is can the sensor be ok, but the board is reading the sensor wrong leading to the UF fault. This would mean replacing the indoor PCB. Normally we find a faulty sensor in these casses, I cant remeber if ive seen a faulty board reading an incorrect temp?

Anyone had a faulty indoor PCB misreading a coil sensor?

Have a good new year everyone.

I have seen faulty boards rather than sensors on refrigeration controls so i expect a similar failure is possible with air con boards.

I have got myself a resistance decade box which you can set to any common resistance to mimic a temp sensor, its handy for diagnosing faulty boards and also for finding out what type of sensor a controller should have if its unknown.

https://www.youtube.com/watch?v=UlwSQUhCUaQ

very nice and practical tool!