LG LSK-244V-3 Split air con won't cool - but does heat OK!

[lee_d]

I have a really frustrating problem which I hope someone can help me with. I'm servicing a LG LSK244V-3 split reverse cycle air con. The problem is that the unit will not cool but it will heat fine. When cooling is selected the compressor turns off, the outdoor fan runs occassionaly, the indoor fan runs as normal, then after about 5 minutes the entire unit switches off and display 6 flashes of the indoor and outdoor power LED.

I have checked the following:
* Basic stuff, fuses, connectors, visibly damaged components on all PCBs etc.
* Compressor is OK. (confirmed by DVM and also the fact that heating is OK).
* Reversing solenoid and slider OK.
* Voltage to the compressor is OK and balanced.

Any suggestions at all?

cheers - Lee

[Yuri B.]

Hello
My conjecture - as 6 flashes seems to be inverter seeing too big current - something seriously wrong with the compressor: it requires from it little effort to run in the heat mode, but it is more hard to it in the cool mode (even just starting).

[charlie patt]

sensors mate they are reading bad resistance and thinks its cool enough whats ambient there

[lee_d]

Hi Charlie, its ~20C (~70F) here in Sydney. Sensors crossed my mind too. I checked the indoor thermisters (2, one air and the other on the evaporator). Both appeared to be in spec but I do need to recheck this. I haven't checked the outdoor sensors (3 of those). But if it was a sensor and the unit thought it was cool enough, why the shutdown and 6 flashes? This does indicate high inverter current, and by all testing I have done the compressor is fine.

[charlie patt]

the biggest problem i have with lgs is the fault codes or led flashing means nothing they have issues wiyh software so even a hardwire controller showing a code does not always show that fault with lg a lg invertor faults useually start playing up at minus 2 ambient and useually after a shutdown period due to cold oil i would check sensors first

[lee_d]

Thanks for the suggestions Charlie. I'll check out the sensors and post results. Cheers - Lee

[lee_d]

Hey Charlie, I checked the outdoor thermisters and found the condenser coil outlet sensor to be suspect. It was less than 1kohm at 25C. I don't have a spec for it but an educated guess is it should be 5-10k at that temp. So I swapped out the thermister with a 8k2 resistor and ran the unit for a short time in cool mode and all worked well. I don't know why this faulty sensor would have this effect but obviously the LG fault codes, at least in my case, are misleading. Lesson is... KISS. Keep It Simple Stupid, ie check all simple fault elements before digging too deep. REALLY appreciate your help. I'll fit in a new sensor (~$30) and post the result. Happy Christmas to all.........

[charlie patt]

just one tip replace al the sensors or you will be back next month/ we have a company policy on lg ignore the codes and replace sensors as a set not on there own just as the customer gets your last bill another sensor will go the sensors are the same resistance but different plugs and length soyou can swap sensors ta charlie

[lee_d]

Hey Charlie, don't know if you'll read this BUT... I've finally installed the new sensors - long story as to the delay, not important... Anyway - all works as like new! Thanks so much for your help. Guys like you are too often under-appreciated and experience dismissed as not needed etc. Well after all, its cheaper for service companies to swap out PCBs etc in the hope of discovering the problem than to actually diagnose the fault. In this case, the original service company (Frost Aust.) wanted to sell the customer a new system because they indicated parts were not available. As it turns out the air-con is running well for less than $100. So once again - thanks from 'down under'. Leigh

[Tayters]

the biggest problem i have with lgs is the fault codes or led flashing means nothing they have issues wiyh software so even a hardwire controller showing a code does not always show that fault with lg a lg invertor faults useually start playing up at minus 2 ambient and useually after a shutdown period due to cold oil i would check sensors first

I have come across a few LG's cooling but not heating. No codes, just no heating. Fault due to outdoor air thermistor out of spec and reading too high a temperature. Unit decides no need to heat as it thinks outdoors is warm but thermistor not open/shorted to generate a fault.

With regards to the 6 flash, DC current code, but fault is thermistor, why is this generated? Is it just due to the fact of poor programming?
Also with ambients of -2*C and lower this code is generated by the extra startup load caused by the thicker oil at these temps I presume?

Cheers,
Andy.

[Tayters]

Just if anyone is interested found this info out about the DC error code.

The code is generated if:

Operating current of IPM exceeds a certain value (35A in the manual I was looking at) and reoccurs a certain amount of times in an hour.

or

DC voltage falls below a certain value (140V - same manual) and reoccurs a certain amount of times in an hour.

or, and easist to catch you out

Temperature of 'outdoor pipe' (I presume condneser pipe) over 65*C whilst compressor is operating and reoccurs so many times in an hour. This is interpreted by system as outdoor fan locked and seeing as it's a brushless motor using the inverter DC supply same DC error code is generated.

Cheers,
Andy.