Daikin Split RKS71BVMB U2 FAULT

[moondawn]

Hi all,
been to a faulty daikin split today,which had a u2 fault.
I was sent to change the following:
PCB 1 (main outdoor pcb)
PCB2 (power supply PCB)
Service monitor PCB
And a SPM board.

fitted all the boards listed above, The only board i did not change was the MID board which is screwed down onto the SPM board. (this has the large capacitors attached to it and gives power to compressor and fans).
After fitting all this i started the system up and got the same fault as previous engineer a U2 fault.

The indoor unit is a wall mount with hand held remote, checked the fault code was u2 by use of indoor remote controller.

I checked i was getting 240 v to outdoor unit and was also getting a fluctuating 40v dc from interconnecting cable 2 and 3.

The condensor seems to have power i then checked the Main outdoor pcb and was getting 240v on to the board between AC1 and AC2 but i was not getting power at h1 and h2 where cables yellow and blue go to the diode bridge.

if i reset the power however i get voltage at point h1 and h2 but this then subsides within a minute or so.

please can someone help as to what to check, does it sound like the new pcb i put on is faulty?

What checks can i be doing?

I have uploaded pics of the wiring diagram maybe some one can help me.

cheers

[tareg70]

Hi pal i had the same problem amoth ago , u need to relace the inverter(not the converer pcb) pcb inculuding the capcitor.Make sure the COMP and the FAN are ok.
good luck

[moondawn]

hi mate, i changed the spm thats the power module but the mid board which screws to it was not changed, this has the capacitors on do you mean that part (The MID board).

[tareg70]

hi pal yes the MID ,BUT MAKE SURE THE FAN IS OK

[slavex]

I had this problem before 1 year, changed all the electronics but had the same alarm. The problem was the fan.

[moondawn]

u2 fault mentions nothing about fan or compressor in the manual, i got daikin saying if the fault does not flash straight away then its the compressor which is what the unit is doing, my instincts tell me the mid board and then sounding like could be the fan also.

how am i to check the fan is okay, i span the fan impeller it turned did not feel restricted but i did not feel it span as long as i would have expected, but that alone was not enough to say faulty fan?

cheers guys for the replies

[Temprite]

You need to check the fan motor with a multimeter

[moondawn]

fitted mid board and switched on the unit then there was a burning smell from the outdoor again no response from the unit, quickly turned off isolater, but later realised it had tripped the mains MCB.

spoke to daikin they reckon the compressor, i asked them for assistance in checking the fan but he said his computer has locked up and would phone me back, unfortunatly he never did.

so now have a possibilty of damaged boards again and looks like either fan or compressor is causing this.
going to mega the compressor and also fan motor if this is possible.

[brunstar]

do not mega the fan motor as it has a printed circuit board in it!!

[moondawn]

okay thanks for the info brunstar. do you have any info for testing whether this motor is okay or faulty?

[brunstar]

you can check the resistance of the motor usually between pins 1 and i think it is 4 on the motor. there is i think 7 terminals and the numbers start from 1 being the end with most cables connected. I think it is 7 pins but 2 pins not used so the cable on its own is number 7.
Get the resistances and Daikin technical should be able to give you the values.
The other check you can do is with the power off and the fan motor unplugged, remove the blade and try to turn the motor anti clockwise to see if there are any lumps or bumps in the motor.

[moondawn]

i started to take resistances and had daikin phone me back, but he was unable to give me any info as his computer froze, he said would ring back but unfortunatly did not.

[Tayters]

Hi Lee,

Out of the 5 wires, there is a hall sensor, power to the motor and a voltage signal from the PCB to signal what speed the motor should run at. Bear with me and I'll try and find the details.

Cheers,
Andy.

[Tayters]

Hi Lee,

Found this for checking the fan motor. Pretty much the same info as I have on paper but saves me writing it up.

http://extranet.daikin.co.uk/en/docu...m219-41003.pdf
The fan motor bit is right at the end but I'm not sure where you can check to see if the actual motor windings are shorted. There is a bit of electronics in the way so I'm not too sure if it can be done unless someone more enlightened knows how.

Could you power up the unit with compressor and fan motor disconnected? Then if anything your U2 code would be changed for the relevant compressor/fan motor code and would prove that part is fine.
Next then the compressor can be meggered and windings tested, then the fan motor checked. I don't know a way of testing components and proving they are seized before powering them up. Hopefully you can plug one component in at a time and get them running. If no go fingers crossed it wont have knackered the new PCB in the process, let's hope the Daikin guy has managed to unfeeze his computer!

Cheers,
Andy.

Edit: Looks like Frank has enlightened me(thanks!). Found a file that he posted a while ago. Not quite your unit but I would imagine the resistance readings would match. Can't get it to insert here so I'll email it to you.

[moondawn]

hi andy, cheers for your reply, think that will be next step unplug fan and compressor and try the system without but i got a burning smell last time so i fear some boards will be damaged i checked the fuses on board of the main pcb they were fine but untill i do what you said i guess i will not know,
if you could email me that file that would be great

many thanks

lee

[Tayters]

Hi Lee,

I sent the file to the address on your Vcard. If you've got a different one then PM me the address and I'll step to it.
I did try to load it here but it was a .docx file which wouldn't upload.

Cheers,
Andy.

[Tayters]

Yay, cracked it!

RZQ(S)71-140 fan checking.doc

[tareg70]

Hi Pal concentrate in your fan and COMP before u install any new pcb MAKE SURE THEY ARE OK ....DO NOT INATALL YOUR NEW PCB BEFORE YOU CHECK THE COMP AND THE FAN

[moondawn]

hi andy thanks for your efforts in getting me the fan checking document.

tareg yeah defo will unfortunatly i feel that the burning smell has taken a board out, the control board i removed again and checked there was no burning marks on it and all on board fuses were okay i think the mid board may have blown or spm board.

many thanks all