Fujitsu blowing multiple boards

[Northy303]

Working on a Fujitsu aoyg30lat4 with 3 cassettes running off same condenser.
1st repair found communication error and blown controller pcb, meggard compressor and fan motors all ok so swapped board and blew straight away.
Rang Fujitsu and were told to replace fan motor and board it then ran for a bit but only on 1 circuit, rang Fujitsu and was told to try swapping ee valve heads around and then the board blew was told by Fujitsu that it shouldn't as it is low voltage.
We then tried changing all EE valve heads and new board and blew again instantly where the EE valves are plugged into the board.
This unit is less than a year old and Fujitsu don't really want to help and I am lost.
And the customer and my boss are getting annoyed.
Any help will be appreciated.
Thanks in advance
Matt

[Tayters]

Hi Matt,
Warranty should be with the wholesaler you got the system from so might be worth speaking to them.
Otherwise I'd confirm no wires are rubbed through (seen similar to yours but coil probe cables short to earth due to rub through).
Valves for B, C and D are on a little bit of extended loom, A plugs straight in.
EEV heads are easy to test, red/orange, red/white, brown/blue, brown/yellow all the same, 45ohms.
If you can see where the board blew, speak with Fujitsu/wholesaler to get them to check the schematics to help pin down what circuit on the board blew to narrow down what part you need to concentrate on. That's how I figures out the case above.
Was it just chance it blew when EEV's plugged in. Perhaps you have issues with another PCB which is causing the other PCB to blow?

Cheers,
Andy.

[Northy303]

Hi Matt,
Warranty should be with the wholesaler you got the system from so might be worth speaking to them.
Otherwise I'd confirm no wires are rubbed through (seen similar to yours but coil probe cables short to earth due to rub through).
Valves for B, C and D are on a little bit of extended loom, A plugs straight in.
EEV heads are easy to test, red/orange, red/white, brown/blue, brown/yellow all the same, 45ohms.
If you can see where the board blew, speak with Fujitsu/wholesaler to get them to check the schematics to help pin down what circuit on the board blew to narrow down what part you need to concentrate on. That's how I figures out the case above.
Was it just chance it blew when EEV's plugged in. Perhaps you have issues with another PCB which is causing the other PCB to blow?

Cheers,
Andy.

Thanks Andy,
I phoned Fujitsu again and wanted to see a photo of the blown board and confirmed that it was expansion valve a but they had never seen this before and they have sent me a valve head and new board and I am fitting it tomorrow I will let you know if it goes bang again valve a was actually the only one we did not replace as it worked but I will do the resistance check first.
Thanks again
Matt

[Northy303]

Thanks Andy,
I phoned Fujitsu again and wanted to see a photo of the blown board and confirmed that it was expansion valve a but they had never seen this before and they have sent me a valve head and new board and I am fitting it tomorrow I will let you know if it goes bang again valve a was actually the only one we did not replace as it worked but I will do the resistance check first.
Thanks again
Matt

Quick update
Expansion valve head and boards changed
Now all working
Thanks Andy.
Matt

[Tayters]

Chest out and strut, good work that man. :-]