Dakin 4MK

[jaav]

G,day all.

I Have a 4MKD90BVMA running 3 outlets, one is a FKD508VMA and the 2 smaller units I cant read.

This unit is in my own house and have had 3 diferent Techs look at it so far.
It 1st shutdown during a heavy rain night with the LEDs flashing. I reset the mains power and it ran for the rest of the night. In the morning it shut down again (flashing),reset the mains and it ran for an hour then flashed a F3 code. Reset again and this time it poped a cct breaker.

The tech came out and found the Inverter PCB had popped the FETs, so he fitted a spare one, the unit ran but came up with a U4 code. he could do a forced cooling run at the start, U4 was still active.
The main control PCB had signs of water sitting on it and had salt corrossion on the componets. I tried to repair but had too much damage. The PCB was replaced and still had a U4. can not do a forced start now.
The Main, inverter (again) PCBs, condenser fan motor, interconecting PCB and one of the small outlet unit PCBs replaced. The coms wiring has been tested.
The Tech just put his hands up and he gives up after 2 days. the next 2 rechecked every thing and cant find the fault. the only thing he did find was 50v coming down the coms wire with all ends disconected. I suspect its just capasitance across the lines.
I ran the outlet units just in fan mode, the large one FKD508 LEDs flashes U4 straight away one of the smaller one ran for 20 min then flashed U4 and the other one showed no fault untill cooling was selected..

Any one have any ideas that the guys may be missing?
Thanks Jim

This unit is now down for 2 weeks and the trouble and strife is driving every body up the wall..

[frank]

Have you checked that all of the indoor pcb's are OK?

U4 means that the indoor & outdoor pcb's can't communicate

[jaav]

Both smaller indoor unit PCBs were replaced and the main one removed from the system.

[VRVIII]

G,day all.

I Have a 4MKD90BVMA running 3 outlets, one is a FKD508VMA and the 2 smaller units I cant read.

This unit is in my own house and have had 3 diferent Techs look at it so far.
It 1st shutdown during a heavy rain night with the LEDs flashing. I reset the mains power and it ran for the rest of the night. In the morning it shut down again (flashing),reset the mains and it ran for an hour then flashed a F3 code. Reset again and this time it poped a cct breaker.

The tech came out and found the Inverter PCB had popped the FETs, so he fitted a spare one, the unit ran but came up with a U4 code. he could do a forced cooling run at the start, U4 was still active.
The main control PCB had signs of water sitting on it and had salt corrossion on the componets. I tried to repair but had too much damage. The PCB was replaced and still had a U4. can not do a forced start now.
The Main, inverter (again) PCBs, condenser fan motor, interconecting PCB and one of the small outlet unit PCBs replaced. The coms wiring has been tested.
The Tech just put his hands up and he gives up after 2 days. the next 2 rechecked every thing and cant find the fault. the only thing he did find was 50v coming down the coms wire with all ends disconected. I suspect its just capasitance across the lines.
I ran the outlet units just in fan mode, the large one FKD508 LEDs flashes U4 straight away one of the smaller one ran for 20 min then flashed U4 and the other one showed no fault untill cooling was selected..

Any one have any ideas that the guys may be missing?
Thanks Jim

This unit is now down for 2 weeks and the trouble and strife is driving every body up the wall..

Hi,

Have you checked the condenser fan motor?

Turn off power to outdoor.
Disconnect condenser fan motor .
Switch power back on.
Check if the U4 clears.
When you try to operate the unit you should get an E7 error.
If you still have U4 comms error the fan motor is OK

Never disconnect/reconnect fan motor when unit is operating.

[Brian_UK]

As an aside - "salt on the PCBs"

It might be worth while getting some spray laquer to seal the PCBs.

I've have to do this on some units near to sea.

[jaav]

Thanks Brian.
There was an E7 as well, the motor has been replaced, as stated in post.
The PCBs now are laquered...

[Temprite]

G,day all.

I Have a 4MKD90BVMA running 3 outlets, one is a FKD508VMA and the 2 smaller units I cant read.

This unit is in my own house and have had 3 diferent Techs look at it so far.
It 1st shutdown during a heavy rain night with the LEDs flashing. I reset the mains power and it ran for the rest of the night. In the morning it shut down again (flashing),reset the mains and it ran for an hour then flashed a F3 code. Reset again and this time it poped a cct breaker.

The tech came out and found the Inverter PCB had popped the FETs, so he fitted a spare one, the unit ran but came up with a U4 code. he could do a forced cooling run at the start, U4 was still active.
The main control PCB had signs of water sitting on it and had salt corrossion on the componets. I tried to repair but had too much damage. The PCB was replaced and still had a U4. can not do a forced start now.
The Main, inverter (again) PCBs, condenser fan motor, interconecting PCB and one of the small outlet unit PCBs replaced. The coms wiring has been tested.
The Tech just put his hands up and he gives up after 2 days. the next 2 rechecked every thing and cant find the fault. the only thing he did find was 50v coming down the coms wire with all ends disconected. I suspect its just capasitance across the lines.
I ran the outlet units just in fan mode, the large one FKD508 LEDs flashes U4 straight away one of the smaller one ran for 20 min then flashed U4 and the other one showed no fault untill cooling was selected..

Any one have any ideas that the guys may be missing?
Thanks Jim

This unit is now down for 2 weeks and the trouble and strife is driving every body up the wall..

Does the outdoor control PCB have a flashing green LED indicating PCB health? From memory the LEDS may be located on a smaller board coming off the control PCB on that model.

Has the compressor windings been checked?

[jaav]

Does the outdoor control PCB have a flashing green LED indicating PCB health? From memory the LEDS may be located on a smaller board coming off the control PCB on that model.

From the last update the green was flashing only. so no problems..

Has the compressor windings been checked?
Yes

A Q for you guys.
If the inverter PCB fails do you replace the Main controll PCB as well?

They now want to replace the whole unit. Told that all the PCB's should have been replaced 1st. now they have 2 blown controll PCB's..

[VRVIII]

Hi,



the only thing he did find was 50v coming down the coms wire with all ends disconected

Could you explain what you mean by this, which cables or cores were connected/disconnected and between which cores or terminals you had 50v.



now they have 2 blown controll PCB's..

Which PCB’s are blown, indoor or outdoor main pcb or ?

[jaav]

The Tech had the comunication wires disconected at both ends for all 3 outlets, he brushed up against 1 of them and got a tinggle then found that they had 50v ac to earth in them.


now they have ordered another main (controll) and inverter PCB for the outdoor unit..

[VRVIII]

The Tech had the comunication wires disconected at both ends for all 3 outlets, he brushed up against 1 of them and got a tinggle then found that they had 50v ac to earth in them.


now they have ordered another main (controll) and inverter PCB for the outdoor unit..
Hi Jaav,

Sorry don't I fully understand what you mean?

The mains and interconnecting cable must have a separate cable for each.
3 core Mains cable live, Neutral & earth

4 core interconnecting cables for each indoor (circuit A/B/C/D)
1 = Live
2 = Neutral
3 = Comms signal
4 = Earth

If you disconnect comms signal (3) at indoor or outdoor you will have fluctuating voltage from both indoor & outdoor.
However if you disconnect at both ends you should obviously have 0 volts on cable core 3.
Are you using a multi core cable to feed various indoors or indoor & mains? If you have voltage I would suggest you install a temporary interconnecting cable (just pass through window) and re test.
Have you checked for voltage between Neutral & Earth?
Do you have a condensate pump(s) wired into indoor(s) if so try disconnecting them.
Do you have a green LED flashing on all indoor & PCB’s?
Do you have local isolators at each indoor? is wire 3 switched?
Have they metered out the compressor?

[taz24]

The Tech had the comunication wires disconected at both ends for all 3 outlets, he brushed up against 1 of them and got a tinggle then found that they had 50v ac to earth in them.


now they have ordered another main (controll) and inverter PCB for the outdoor unit..


Hi Jaav,

Sorry don't I fully understand what you mean?

The mains and interconnecting cable must have a separate cable for each.
3 core Mains cable live, Neutral & earth

4 core interconnecting cables for each indoor (circuit A/B/C/D)
1 = Live
2 = Neutral
3 = Comms signal
4 = Earth

If you disconnect comms signal (3) at indoor or outdoor you will have fluctuating voltage from both indoor & outdoor.
However if you disconnect at both ends you should obviously have 0 volts on cable core 3.
Are you using a multi core cable to feed various indoors or indoor & mains? If you have voltage I would suggest you install a temporary interconnecting cable (just pass through window) and re test.
Have you checked for voltage between Neutral & Earth?
Do you have a condensate pump(s) wired into indoor(s) if so try disconnecting them.
Do you have a green LED flashing on all indoor & PCB’s?
Do you have local isolators at each indoor? is wire 3 switched?
Have they metered out the compressor?


Hi Jaav.

I agree with VRVIII, if you have voltage down the coms when disconected then there is somthing wrong with that. I would rig a temp control circuit also to prove if ok.

taz.

.

[brunstar]

there is either induced voltage in that cable or mixed circuits by the sounds of it.
If you are using a 3 core and earth you may have transposition between the comms and the neutral and this is earthing the communications which would give you the U4.

The other possibility is that if you have corrosion you may have excessive corrosion on the terminal block causing high resistance.
I would try one unit connected at a time.

This still does not explain the 50 volts and tingles????

[jaav]

The mains and interconnecting cable must have a separate cable for each.
3 core Mains cable live, Neutral & earth
the wiring is 3 core plus a single for comms.

4 core interconnecting cables for each indoor (circuit A/B/C/D)
1 = Live
2 = Neutral
3 = Comms signal
4 = Earth

If you disconnect comms signal (3) at indoor or outdoor you will have fluctuating voltage from both indoor & outdoor.
However if you disconnect at both ends you should obviously have 0 volts on cable core 3.
Are you using a multi core cable to feed various indoors or indoor & mains? If you have voltage I would suggest you install a temporary interconnecting cable (just pass through window) and re test.The comms wire is removed at both ends. All indoor units are disconected.
Have you checked for voltage between Neutral & Earth? Yes. close to zero
Do you have a condensate pump(s) wired into indoor(s) if so try disconnecting them.N/A
Do you have a green LED flashing on all indoor & PCB’s? all but one in fan mode. once cooling is selected they all flash U4
Do you have local isolators at each indoor? is wire 3 switched? NO
Have they metered out the compressor? YES

[jaav]

The other possibility is that if you have corrosion you may have excessive corrosion on the terminal block causing high resistance.
I would try one unit connected at a time.
The terminal block has been replaced.

This still does not explain the 50 volts and tingles????
Not yet.

[VRVIII]

The other possibility is that if you have corrosion you may have excessive corrosion on the terminal block causing high resistance.
I would try one unit connected at a time.
The terminal block has been replaced.

This still does not explain the 50 volts and tingles????
Not yet.
This could be caused by:

Routing interconnecting cables along side power cable, this can result in induced voltage in your cable. Power cables must be kept away form interconnecting cables.
Could there be any joint/junction boxes in the interconnecting cable? The box could be filled with water or have a loose connection.
The units must be wired 123 outdoor to 123 indoor, no star connections or separated power supply.


the wiring is 3 core plus a single for comms
Why was a 3 core cable used? I would recommend this be replaced with a 4 core or at least use the 3 cores for 123 connections and the single core for earth.



would suggest you install a temporary interconnecting cable (just pass through window) and re test.
Have tried operating the system with only one indoor connected and interconnecting cable replaced with temporary 4 core?

[jaav]

last report today is that Dakin have agreed that the New Controll PCB is faulty. So Its a waiting game again.

[VRVIII]

last report today is that Dakin have agreed that the New Controll PCB is faulty. So Its a waiting game again.
I’m not convinced, unless the real problem has also damaged the new PCB.

[jaav]

Well The AC is back on..
The replacement Tech fitted the PCB, Got the unit to do a forced run.
Still showing up U4 on 2 main outlets. He found the system would run on the smaller outlet, then alarm bells started ringing. On the 2 other outlets with U4, the Active and Neutral are reversed at conection board. In some wisdom Dakin changed the 2 around so it was different to the small outlet and outdoor unit. The other Techs I suppose were just in auto mode wiring them up as the rest. Its the simple things that get you..
Thanks guys.