Fujitsu AOY30TMBDL Help Please!

[runningonavac]

Fujitsu AOY30TMBDL. Error Code E:01 = Communication between indoor/outdoor unit. Found T3.15a Fuse blown on outdoor pcb. Board looked knackered and burnt so replaced board. Plugged one thing back in at a time on board and powered up. Last thing to plug back in was the transformer, power up and pop goes 3.15a pcb fuse. I unplugged both connections from tranny to pcb, replaced fuse on pcb and power on - no popped fuse. I plug in the 2 purple leads from tranny into pbc and power on - no popped fuse. Once the other plug from the tranny is plugged into board the fuse pops, suggesting tranny is at fault. I have tried 2 other known to be ok trannys, and the fuse keeps blowing! Any ideas anyone? Many thanks in advance...............;)

[nike123]

It is probably fault at PCB. Unplug everything except transformer and PCB and try again.

[runningonavac]

Isn't the tranny just for the main power relay coil? (12v)

[nike123]

Isn't the tranny just for the main power relay coil? (12v)

No, it is also power supply for outdoor PCB (5V and 12V)

[runningonavac]

It is fine until the transformer's 2 red wires (pressuably the low voltage supply) is plugged into pcb. Tried 2 other trannys - still the same.

[nike123]

It is fine until the transformer's 2 red wires (pressuably the low voltage supply) is plugged into pcb. Tried 2 other trannys - still the same.

Did you or did you not unplugged everything else from PCB?
If you are, than PCB is faulty!

[Robin]

Tranny supplies low voltage (5, 12 & 24v to PCB. If the fuse is still blowing then a low voltage function is shorting out. Fuse only blows when tranny supplies power to low voltage.