Daikin Ducted Type Indoor Unit FDMG36NUV2S

Abnormally high pressure level is mostly caused by the condenser side.

The following contents are provided by service engineer based on their field checks.

Further, the number is listed in the order of degree of influence.;

Warning: Do not touch the energized part (high voltage part) for at least 10 minutes after the power is turned OFF.

Be sure to touch the earth terminal with a hand to release static electricity from the body (to prevent PCB from being damaged).

Residual electric charge of the power transistor (should be DC 50V or less)

Remove the wire connecting the power transistor and the compressor. Remove it from the compressor terminal side. Be careful not to deform. Faston terminal at the end of the relay wire.

Resistance measurement for phase 1

Resistance measurement for phase 2

Resistance measurement for phase 3

Is the resistance value equal to 5 times or more than the other resistance values?

Diagnosis of inadequate refrigerant in cooling operation

Suction superheated degree increases due to refrigerant shortage

Decreased evaporator capacity caused by refrigerant shortage

Compressor frequency decreases despite a large difference between temperature set by the remote controller and suction air temperature

If refrigerant shortage worsens, the electronic expansion valve remains fully open and suction superheated degree further increases

Diagnosis of inadequate refrigerant in heating operation

Suction superheated degree increases due to refrigerant shortage

Compressor frequency decreases because suction superheated degree is controlled to prevent oil to the outdoor unit heat exchanger from being retained

Evaporator capacity and compressor frequency decrease despite a large difference between temperature set by the remote controller and suction air temperature

Check for Fan Motor Connector (Signal Line)

(2) With the fan motor connector disconnected, measure the resistance between each pin, then make sure that the resistance is more than the value mentioned in the following table.

(2) With the fan motor connector disconnected, measure the resistance between each pin, then make sure that the resistance is balanced in ±30%.

Check for Fan Motor Connector (Power Supply Line)

With the relay connector disconnected, measure the resistance between UVW phases of the connector (3 cores) at the motor side, then make sure that the resistance between each phase is balanced and not short-circuited.;

As criteria for judging whether refrigerant is excessively charged or not, refer to the following operating conditions.

<Diagnosis of excessive refrigerant charging>

(1) Because high pressure rises due to excessive charging, overload control is carried out and capacity tends to run short.

(2) Considering pressure load, compressor discharge pipe temperature is low.

(3) Subcooling degree of condensate liquid becomes large. Therefore, temperature of blown air passing through subcooling part decreases in heating operation.;