Problem with lg multi split fm25ah

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The issue is that randomly say 2/4 indoor units will not call for cooling despite there being a demand. The outdoor unit operation icon doesn't show up on the controller and the compressor doesn't run. A power reset at the mains will rectify this, then it could change to 1/4 units that won't operate or 4/4 units will run for a short time then similar issue occur.


There is no way to get it to call for cooling even turning on and off at the wired remote and resetting the controller does nothing.


My upstairs units have been running all night this morning I've gone down to turn the lounge unit on, it turns on etc, fan blows set point is 21c room temp is 23.5c on the controller and it will just not talk to the outdoor unit or call for cooling it seems. There are no error messages displayed on both outdoor or indoor sides.


Thing is if I power reset it at the breaker it will all will work for a bit then it might be a different unit that doesn't operate properly the next time I come to operate them and it's been turned off a bit. Very confusing to say the least. I've recently downgraded all indoor sub pcb's to 7000btu from a mix of 12 and 9000btu units. They all operate at one point ok, however one board last week when fitted caused various features to stop working on that said unit and would then not operate or call for cooling. Assumed that this sub board was faulty and swapped back to the 9000btu while awaiting a replacement to come. Since then the issue has been spread around the system I do hope that the dodgy sub board hasn't caused a short on the outdoor pcb. I've even changed the indoor pcb on the original affected unit to ensure that it wasn't a dodgy indoor pcb wasn't causing issues.

There are no fault codes displayed so I am unsure as to what the issue could be.

Thank you.

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Still haven't managed to sort this...

The issue is that randomly say 2/4 indoor units will not call for cooling despite there being a demand. The outdoor unit icon doesn't show up and the compressor doesn't run. A power reset at the mains will rectify this, then it could change to 1/4 units that won't operate or 4/4 units will run for a short time then similar issue occur.

My upstairs units have been running all night this morning I've gone down to turn the lounge unit on, it turns on etc, fan blows set point is 21c room temp is 23.5c on the controller and it will just not talk to the outdoor unit or call for cooling it seems. There are no error messages displayed on both outdoor or indoor sides.

Thing is if I power reset it at the breaker it will all will work for a bit then it might be a different unit that doesn't operate properly the next time I come to operate them and it's been turned off a bit. Very confusing to say the least. Strange thing is when you turn one of the units off the others will usually then run cooling ok it's as if the units that are running are locking up the comms signal but there are no errors at all.

It seems to be when the kitchen unit is running... If that's on it stops the others calling for cooling. As soon as I turn that one off any others that were calling for cooling will then immediately get cooling. The little outdoor unit operation icon doesn't show up on the controller despite that unit calling for cooling the EEV just doesn't seem to open or it doesn't get the signal. As soon as that unit is turned off the others will work, so confusing. It's as if the signal is being blocked. Outdoor unit ramps up as knows there's demand but EEV will only open when one of the others goes off. Yeah am wondering what it is this issue may have been here for ages but with the indoors all being small now rather than 3.5kw they don't cycle off and keep running which is better. Before they would cycle off quite often so giving control to other units calling for cooling

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The blue red white & black comms cables are all touching the mains power coming into the pcb off the connecting block and wrapped round could this cause interference in the signals etc? Ok now working fine in cooling & heating and just tried to confuse it by turning all on/off randomly and still worked ok so I am wondering if all the data comms cables touching the power supply cable into the outdoor unit was causing interference so too many signals were going down at any one time. Remember this wasn't indoor unit specific it could happen on any unit or units at a time...

[Gideon Beddows]

Don't know a lot about LG , but if the comms cable is not screened then there is every chance you are getting noise transmission through the cabling? 1's becoming 0's and vica-versa? If its not screened and no-one else has any suggestions, then I'd change the cable?

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The issue is there are 4 cables... Do u mean the interconnecting cable from each indoor unit or do u mean the 4 comms cables that link from the outdoor pcb to where the comms cables come into the outdoor unit from the indoor units?

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Ok tidied up wiring etc. Still same issue now we have disconnected a&b and seeing if the issue shows it's self when the upstairs ones are not connected up. We're starting to think outdoor unit pcb fault.

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This is now looking like an outdoor pcb fault even though no errors are showing up. With one indoor in cooling and the other 3 turned off compressor can be seen to ramp up to 1.8kw input when only a 2.1kw indoor unit is turned on. It shouldn't even get that high with all 4 indoors turned on and in full cooling. There is only 1 pcb in the outdoor unit quite possibly this has never been right from installation. This leaves the noise of refrigerant fiercely flowing around the system.

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Hey all its me again, hope to get some replies this time if anyone can help.

We are now having to reset the power at the breaker to get the indoor units cooling. Indoor units call for cooling (we know this as compressor ramps up) but eev doesnt open to supply refrigerant to indoor. We know the EEVs are working as a power reset at the breaker means it will work for a bit. BUt then we are noticing compressor will ramp down as it should but then the coils stop sweating and room temp starts to rise and it cant maintain the temp. The EEVs should then be opening to let cooling back through but they dont. If we physically turn 3/4 indoor units off and one unit that was calling for cooling but not getting any cooling the outdoor unit continues to run but no refrigerant goes to that unit so the EEV is remaining closed. After a few minutes compressor shuts off as the refrigerant isnt going anywhere then after 3 mins rest time the outdoor unit comes back on and cooling commences on that unit and refrigerant flows. Sometimes you can turn one indoor off and that will then let the eev open on another unit that was calling for cooling sometimes followed by a loud hiss from the valve opening and the pressure equalising across the indoor unit.

If all 4 indoor units were turned on but not cooling we do a power reset for a couple of mins, some of the indoors then dont turn back on whereas they used to do so following a power cut etc and 2 of the wired remotes actually fully reset back to factory defaults such as the time etc whereas they used to remember it for an hour or so... anyway all 4 indoor units will then work ok in cooling until one will reach thermostat off, if that unit should then call for cooling it and the outdoor unit is already running the eev will not open until one of the other indoors reaches thermo off or is possibly turned off completly but compressor ramps up knowing it has extra load. It really is very difficult to describe properly.

Questions is spend £300 on a new o/d board or do you get a new o/d unit? Its from 2008 when it was installed and there have been many times that the bad electrics have caused a trip out and I know there have been power surges to the outdoor unit before. Could this be causing this erratic behaviour on the outdoor unit?

My engineer says impossible to pin down the issue and it could still be an indoor board or boards that are causing the issues. He said the indoor unit tells the outdoor when to run but we know its getting that signal as the compressor ramps up but sometimes the "outdoor unit" symbol on the controller doesnt illuminate and sometimes it does but until that eev opens no cooling commences. Run the system as a 1/1 split with just 1 indoor on and it runs fine, ive tried every single unit individually and even disconnected every other internal unit from the electrical side of things so that the outdoor thinks only 1 is physically connected. I assume the outdoor unit board controls the EEV position based on the information it receives from the indoor boards and the fact these issues happen across all 4 indoor units in no particular order means that all 4 indoor boards cant be faulty so it points back to the outdoor board being faulty. There are also no comms errors or any other codes coming up.

Please help...

[frank]

Have you checked all of the sensors on the system against a Temp/Resistance chart for your unit.
Remember that the pcb's rely on these for information. Wrong information in =Wrong information out.

Why are you changing indoor pcb's for ones with different capacities?

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Outdoor unit sensors were replaced but same issues persist. Indoor sub pcb's were changed on two units as we had 3.5kw before downstairs and it was forever cycling off and poor dehumidification as it reached temp too quick. With the 2.1kw units all indoors are the same size.