LG split system help: fault code CH-02

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Old 01-21-16, 05:09 PM
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LG split system help: fault code CH-02

Hi all, first post, thanks in advance!!

We have an LG LBUG3061YL split system air con system, that is not working properly (error CH02).

Unfortunately its over 10 years old so getting someone to fix it is proving difficult.

My searching has shown CH02 is the indoor unit sensors error, we have replaced them both but it didn't fix it. I then sourced and replaced the indoor PCB again it didn't fix it.

The unit turns on, then runs for a couple of minutes, then when it turns the outside untit on, it runs for a further couple of minutes, then comes up with the error.

I would like to try to trouble shoot more but I don't really fully understand how the system works. There are two electrical cables that go alongside the gas lines from the outdoor unit to the indoor unit in the ceiling cavity.

One I believe simply supplies AC power to the indoor unit from the outdoor unit?

The other I assume is some sort of communication from the indoor unit & control panel, to tell the out door unit to turn on/off? is that correct?

Is that cable simply a voltage (AC or DC) or it some sort of communication like RS232?

Is it feasible to in some way override the communication essentially putting a manual switch on the outside unit to just get it to work. I appreciate it wont be thermostatically controlled but at this stage our summer is currently over 100 degrees F in the day, and 80 at night!!

Again any help really appreciated.
 
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Old 01-21-16, 07:44 PM
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Post the model number of the outdoor unit.
 
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Old 01-21-16, 08:06 PM
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LBNG3061YL / LBUG3061YL

I've been looking over service manual obtained here....LG LBNG3061YL SERVICE MANUAL Pdf

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Old 01-21-16, 08:47 PM
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Thank you for the replies.

That is the model number I believe of the outdoor (and indoor) unit. And in the operators manual that we have that came with the unit it lists CH02 as "inlet pipe sensor" which we have replaced as well as the indoor pcb.

Also after talking to the technician, last week he advised that I may as well try changing the outdoor sensors. So he ordered and supplied them and I did this, one was attached to the piping, the other was cable tied to the outside of the fan grille at the rear of the outside unit. They shared a common plug onto the main board. Still CH02 error code.

Through this 8 week period of trying to solve the issue the main board on the outside unit has also been changed to a new one, again with no success.

It still comes up with CH02.
 
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Old 01-23-16, 04:27 PM
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LG - CH02 Error Help

Hello, posted a question on another thread but I think i have a little more information to hopefully get some help.

LG Reverse Cycle Split Air Conditioning System.
Indoor (roof) unit - LBNG3061YL
Outdoor unit - LBUG3061YL
Approx 10 years old.

Turn on a/c for cooling, system starts for first few minutes as normal, then comes up with a CH02 error on the indoor control panel and the system stops.

Thanks to others, have the manual for the unit and it appears CH02= "Outdoor air or piping temperature thermistor error"

We have changed the thermistors (one sits against pipework in compressor area in outdoor unit, the other is zip tied to the air grille at the back of the unit. Still has same problem.

Have swapped the main outdoor PCB for a replacement new unit, still has same problem.

I have measured the resistance of the two thermistors, and both measure in spec at 5k and 10k respectively (both old and new)

Any suggestions on what to do/try next please?
 
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Old 01-23-16, 07:06 PM
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I combined your two threads here and changed the main title. We keep one topic in one thread.

I don't have any suggestions to try. Houston may.
 
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Old 01-23-16, 07:53 PM
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I have sat out opened up the outdoor unit, and carefully checked through all the connections etc, I cant see anything obviously wrong, burnt, disconnected, or broken.

But I have noticed there are three more thermistors inside the outdoor unit plugged into the main PCB. They are labelled Suction, Discharge and Pipe D. I have measured the resistance value of them at 25 degrees C as follows;

Suction - 5 kohm
Discharge - 75 kohm
Pipe D - 5 kohm

I do not seem to be able to find information anywhere as to what the values of these should be.

Is it worth just replacing these to see if its the issue, at least thermistors are relatively inexpensive and easy to get?
 
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Old 01-24-16, 12:53 AM
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There is a manual that tells you what they should read.
I seem to remember a test button outside that will run each step of operation as you touch it and I had to replace one of these plugs that had 2 sensors outside on an LG. I don't remember what the values were and I seem to be breaking my cell phones recently so I no longer have this manual. The sensor wasn't very expensive.
 
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Old 01-24-16, 09:25 AM
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Suction - 5 kohm
Discharge - 75 kohm
Pipe D - 5 kohm
Looking at those values..... as a guess I'd say the discharge thermistor has a problem. That value is way out of line of all the others.
 
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Old 01-24-16, 03:13 PM
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Yea that's what I thought when I measured it at 75k. All the others thermistors though have pretty light gauge wire and simple PVC tube sleeving. The discharge one though has high temperature white braided sleeving and wire so I sort of thought though maybe its a different temp one to the rest so maybe the 75k was OK.

Just annoyed I cant find anything to tell me what it should be.
 
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Old 01-24-16, 04:08 PM
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I just contacted LG through their technical chat on the website. I am trying to find what the resistance should be of the thermistor, all I got was quote "we do not have that information available anymore"

So I guess my only option is to try and buy one, I guess before fitting it I might measure what it is, and compare it to the current one. Not sure there is anything else I can do.
 
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Old 01-25-16, 06:13 AM
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LG is builder grade. Nothing but issues! I wish you luck in fixing it.
 
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Old 01-30-16, 02:19 AM
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Discharge thermistors are always different from the others because discharge temperatures are much higher. 75k should be ok.

I think the problem is that the unit can't reach the correct suction superheat. It calculates superheat as Tsuction-Tevap (while cooling, evaporator sensor is the one on the pipe in the indoor unit). Superheat should be somewhere around 7 degC. If it's too low or negative, the unit will stop to protect the compressor from pumping liquid refrigerant. Check voltages on these two sensors (in milivolts range - max 5V) while the unit is running. Voltage on the suction sensor must be lower than on the evaporator sensor (higher temperature=lower resistance to ground=lower voltage). If it's not, compare the actual temperatures of the pipes. It may be not an electrical problem.

Does it run correctly in heating mode? Indoor pipe sensor will be ignored in heating mode. If it runs, the problem is in the indoor unit. If not, it's in the outdoor unit or the refrigerant itself.
 
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Old 02-05-16, 08:37 PM
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OK, well we have a resolution (sort of) So I was able to buy replacement discharge and pipe thermistors (but not the suction). When I replaced them I measured the resistances, and the old and new parts measured exactly the same. So I thought to myself, bugger well looks like this wont solve the problem. But I swapped them anyway. And of course bingo, the system works perfectly. So tbh I don't know or understand why. Is it possible that one of the old thermistors wasn't changing with temperature properly? Anyhow, its now working so I am going to leave it alone.
 
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Old 02-05-16, 09:45 PM
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The only thing I can think of is that there was a problem in the connector.
 
 

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