fujitsu outdoor fan not spining fast enough

[Tom 108]

Hi good a/c brains
Fujitsu ao54ujbmr I had faulty compressor ( replaced)
Found that outdoor fan motor wasn't spinning fast enough. Replaced capacitor still not spinning fast.
suction pressure 7 bars
discharge pressure 32 bars fan is pulsing very slow monition, all four indoor max cooing. I have suspicion on main PCB. could anybody help.
many thanks Tom

[matt.yelland]

Hiya Tom,

Not really an a/c engineer, does the unit have a fan speed controller?

[bigor_2]

The compressor cause of defect is defined?

[Robin]

In cooling mode the fan is controlled by the condensing temperature. Once the coil temp gets above 44degC the fan should go to high speed. The coilsensor may be faulty, it should read 4.9kohms at 25degC (unplugged from PCB). Otherwise the PCB may be at fault. If the fan is running too slow the H/P control should stop the unit but it has to fail twice in 20 minutes to cause an alarm message. Check the mid coil temp beside the sensor if lower than 44 degC fan will either be in low or intermittant operation.

[paul_h]

In cooling mode the fan is controlled by the condensing temperature. Once the coil temp gets above 44degC the fan should go to high speed. The coilsensor may be faulty, it should read 4.9kohms at 25degC (unplugged from PCB). Otherwise the PCB may be at fault. If the fan is running too slow the H/P control should stop the unit but it has to fail twice in 20 minutes to cause an alarm message. Check the mid coil temp beside the sensor if lower than 44 degC fan will either be in low or intermittant operation.

How did you even work out the aust equivalent model?
I'd like to help but have no clue from the model whether it's a 3phase old unit or a inverter.
Are you talking about the sensor on the outside of the condenser in a plastic cage, or the sensor inside at the bottom of the coil in a copper elbow pocket?
I always though it was the outside sensor which measures more the ambient temp that controlled fan speed on the 3 phase systems with a/c fan motors.

[jhoger]

possible short in the windings of motor?

[windzer]

bad berings in fan moter maybe