Daikin fault U4. relocated

[Matty whitelock]

Been having such a ****ting time with Daikin floor console.
1. fault U4
2. got it going for a couple of days, then fault U4 occurs.
3. Outdoor unit on temp/supply (flex lead plugged into power socket only).

history: secondhand unit was working prior to disconnection.
I had it degassed and regassed, then cleaned indoor unit washed filters and drum(s) installed at new location. Than all of the above happened.

PLs help:rolleyes::rolleyes::rolleyes::rolleyes::rolleyes:

[frank]

A U4 fault indicates that the transmission signals between the indoor/outdoor unit PCB's is not happening.

If, as you say, it worked fine before it was moved, then I would suggest that the transmission wiring has been installed incorrectly, i.e. the interconnect wire is the wrong specification, the interconnect cable has excess wires that are not earthed at 1 end, the interconnect wiring is adjacent to other cables causing interference, the transmission wire has been 'broken' through a local isolator etc.

Without seeing the installation or knowing the age of the unit or the model number we are just guessing.

My advice would be to run a temporary single wire connection between the indoor pcb and the outdoor pcb on the transmission terminal (No.2 on the old kit and No. 3 on the newer kit) and see if this solves the problem.

[Matty whitelock]

A U4 fault indicates that the transmission signals between the indoor/outdoor unit PCB's is not happening.

If, as you say, it worked fine before it was moved, then I would suggest that the transmission wiring has been installed incorrectly, i.e. the interconnect wire is the wrong specification, the interconnect cable has excess wires that are not earthed at 1 end, the interconnect wiring is adjacent to other cables causing interference, the transmission wire has been 'broken' through a local isolator etc.

Without seeing the installation or knowing the age of the unit or the model number we are just guessing.

My advice would be to run a temporary single wire connection between the indoor pcb and the outdoor pcb on the transmission terminal (No.2 on the old kit and No. 3 on the newer kit) and see if this solves the problem.
Thanks Frank, the outdoor unit model RXD60BVMA, indoor unit FLX60AVMA will try the above right after thread.

[Matty whitelock]

Wiring all correct with 230V between phase and neutral terminals on outdoor unit and interconnect and earth all connected correctly with no isolator. Interesting thing is this...unit works intermittantly (rather than not at all) on another power circuit with voltage of -7.94V on interconnect terminal. On the other circuit which doesn't work at all it shows exactly the same voltages but the indoor unit shows the blinking LED light instead of the solid. Likely cause electrical interference to the PCB? Even when the unit works it shows a blinking LED on the outdoor unit indicating to check the indoor unit. Will dedicate supply to narrow problem down. Are there any known issues with Diakin in relation to this?

[Yuri B.]

http://download407.mediafire.com/jxzhh1hyz3dg/csynpxx3cqy/Service+Diagnosis+Split+Pocket+Book.pdf
Hello Matty. I am not familiar with Daikin AC s but maybe the PDF through this link will be somehow helpful to you.

[frank]

Wiring all correct with 230V between phase and neutral terminals on outdoor unit and interconnect and earth all connected correctly with no isolator. Interesting thing is this...unit works intermittantly (rather than not at all) on another power circuit with voltage of -7.94V on interconnect terminal. On the other circuit which doesn't work at all it shows exactly the same voltages but the indoor unit shows the blinking LED light instead of the solid. Likely cause electrical interference to the PCB? Even when the unit works it shows a blinking LED on the outdoor unit indicating to check the indoor unit. Will dedicate supply to narrow problem down. Are there any known issues with Daikin in relation to this?
The green LED on both the indoor and outdoor PCB's should be blinking under normal operation. The PCB LED blinks at a rate of 1/sec to indicate that the PCB is OK. The second green LED on the indoor PCB blinks/flashes in relation to the data transmission speed