Diagnosing Daikin H3 E3 Error (EP 1)

Daikin Fault Code H3 E3 U2-01

In this video I am diagnosing which part is faulty on a Daikin unit that stops working intermittently. As the unit was running completely fine when I was there, I needed to temporarily make some changes to the wiring as a process of elimination. I suspect the outdoor PCB is faulty but time will tell.

H3 - High Pressure Switch Fault
This is stating that there is a fault with the high pressure switch. This fault occurs when the system is in an off state but is still registering that the high pressure switch is open circuit. The only time the switch should be in an open circuit, is when the system is in a high pressure state.

E3 - High Pressure Switch Activation
This is stating that there has been a high pressure error on this system.

U2 - Outdoor Unit Inverter PCB DC Voltage Shortage
This is an issue with the incoming power supply. It is detected by monitoring the DC voltage on the inverter PCB, and if the voltage on the DC circuit of the inverter is above 700vdc or below 200 vdc it will trigger the fault. The over voltage is due to an instability in the incoming voltage, while this issue could also cause the under voltage, this can also be caused by not having all three phases being switched onto the inverter PCB. This can be due to a fault with the inverter contactor or even the Noise Filter PCB.