Air Conditioning - LG Split System Trips Out

Forgive me if i have put this topic in the wrong area? Moderators feel free to move it! I have a LG model LST243H-2, Heating and Cooling split system air con about 7 years old. It tripped out the circuit breaker 4 days ago! I have tested the 2 capacitors and they come up to specification.(1 motor start cap 90um and 1 dual cap, Hermatic 50 um and condensor fan 6um).I have also replaced the condenser fan motor with a new genuine part.($72.00 AUD) I also inspected and tested the internal electronic circuit board and it seemed fine! I can run the inside fan of the split system all day no worries, but when i switch to air con mode the outside unit is silent,no compressor noise at all, and after 1-2 mins the condenser fan spins for 1- 2 seconds and then trips out the circuit breaker. In this time the condenser coil does not even get warm.I just dont know how to test the compressor and any associated electrical components for this type of unit. I am missing some basic troubleshooting knowledge ! Any replies would be much appreciated. Beer 4U2

Start by replacing the potential relay. This is a likely failure. Its a relay that takes out the compressor during the start cycle, and resets when off. Its likely you had a bleed resister across the start capacitor which unless you temporarily removed it would be unable to test. Some companys don't use one because they run a live wire in the windings for a crankcase heater....anyway... The relay is an electrical switch and prone to failure...and a cheap fix.
A test on the compressor with the ohm meter. First label the three wires on the compressor pecker head. Remove the wires from the compressor. Set the ohm meter to its lowest setting. Measure and write down the values of C to R, C to S and S to R. C to R should be the lowest, C to S should be 3 to 5 times what was read on C to R, and S to R should be the highest and be = to R+S(+/-) .5 ohms. All three terminals to ground should be open (as if touching nothing).

Thanks for your prompt reply hvac01453.
Your right, i had to unsolder 1 leg of the bleed resistor to test the starter cap them re-solder it back on.
When you mention potential relay are you refering to a magnetic contactor? 24 volt, 2pole, 30 amp ?(this is a guess until i can identify the old one, or even find it)
This is what i am currently trying to find in the outside unit at the moment. It not near the 2 caps at the top and im thinking it may be closer to the compressor in the botttom of the cabinet. I will keep looking :wall:

I have looked for a magnetic contactor(potential relay?) but alas there is not one at all ! How can this be ? All i noticed was 3 wires coming from the compressor, red,brown and yellow. red goes to the circuit board (RY-COMP).yellow goes to the herm side of the dual cap. Brown goes to a busbar which in turn goes back to the board(small power transformer 230v-50hz-dc 12v).A wire comes from the board and links directly to the start cap. With the newer air cons have they done away with the magnetic contactor(potential relay) ?
Anyway i have ordered a new electronic circuit board and upon closer inspection the small power transformer on the board 230v-50hz-dc 12v seems a bit dodgy (rust and irregular colouring).
$40 AUD was cheap for this board and i will have it monday.
I will definately let you know how i go!
Once again thank you very much for your inputBeer 4U2

follow the leads from it...one will go to the relay. some don't use the potential relay but a PTC. This part looks like a 2 to 3" barrell about 1.5 " in diameter, with a connection in the middle and one on each end of the barrell. Just follow the leads froim the cap...
Kill the power and Remove the compressor cap covering the leads and make sure they are connected also.

Yea,... the circuit board is getting to be more common than ever. all the switching is done electronically. Before you remove wires from the circuit board use a digital camera and take a few snaps. Thats a cheap board for sure! many of the problems are apparent once you remove the board and see the backside, but not always. Hopefully you don't have to replace the compressor. Do the check with the ohm meter on the compressor reguardless.

hvac01453 thanks again for your input!
Without your assistance this site and many like it would not exist! Credit given when credit due!
I will definately let you know about the board replacement and
also test the compressor.
thanks from a brewery worker.Beer 4U2Beer 4U2

Replaced the new board and it still tripped out ! So i checked the 3 wires coming from the compressor and they were partially corroded and sort of melted and 1 wire was completely corroded away(green copper rust) from its terminal.I renewed the terminals and sprayed lanolin over the contacts to minimise further corrosion. So i thought maybe it wasnt the board and swapped the old one back in. It didnt trip, but the compressor would not start so i put the new board back in and it worked first go.Now it appears to cycle on and off regular (like it should do)where as before the compressor would just run nonstop.Beer 4U2

sounds like your cookin with gas!....Good luck!

hvac01453
Trouble brewing again ?

Air con been working nice and cold for 3 days, it was perfect!
All of a sudden it was intermittent with icy cold to warm air,then it started blowing fuses again. Checked the wires leading to top of compressor and the red 1 was burnt out again touching a brown wire it had slightly melted through.
So I separated all 3 wires well apart so they would not trip off the circuit breaker and left the plastic cap off the wires on top of the compressor.Turned on the air con and it didnt trip and was icy cold as well but didnt like the look of the glowing red pin on top of the compressor.It was that hot you could see it glowing with heat generated from the R pin(also red wire)C and S pin okay as long as wires kept away from R PIN.
Test on Compressor =
C TO R 000.9 ohms, C TO S 001.6 ohms, S to R 002.4 ohms.
Wires to compressor 14AWG, 105 degrees , LG original wires.
Any Ideas ? Thanks in advance

follow the wires from the compressor back to wherever they go (opposite end and read the voltage from there simply because its too hard to read from the compressor in many instances. first read from the C and R terminals , Then the C and S terminals, They should be what the supply voltage is within reason (10%). I would replace the run cap if you haven't already simply because they are cheap and can cause high amp draw. Do you have an amp meter?

Hope you don't mind me breaking in on this thread. Have a similar problem with an LG LS-K2463HL split system.

Initial problem was that it tripped the RCD (safety switch). Was too dark and hot to play with it so turned the A/C breaker off and left it for the night. Tried it again next night - RCD didn't trip, but fan wouldn't spin up. Compressor would grunt away for exactly one minute before it would shut down. System is fully gassed - it's not tripping on low pressure.

Thought the problem might be the condensor fan motor starter cap, so replaced the starter cap and condensor fan motor (was getting on in years and a replacement was cheap).

Fired it up again after fitting the new gear. Now the fan kicks when the compressor comes in but won't rotate. Give it a flick by hand and the fan will run from that time on, but not at anywhere near normal speed.

Likely culprit the dual cap? Unfortunately the local distributor will have to order the dual cap in for me (3-4 weeks) and couldn't find the soft start circuit board on their system at all!

Any advice appreciated :)

http://i207.photobucket.com/albums/bb259/tim_sarah_w/IMG_0669-1024.jpg

dont use a dual cap! buy two separate caps they are cheaper.
Pauly3571- the glowing red pin is a NO-NO. Amp the R leg of the compressor. Install new wires from the compressor to the other end where they connect. Read the voltage from C and R. This should be within 10% of the rated voltage. Check also to see if the compressor is grounded. With leads removed on compressor, ea pin to ground, if there is any at all, the compressor is toast. This is normally done with a megohmmeter but you won't have one of those..., so try those tests.

hvac01453
Compressor grounded electrically, therefore, dead. I had a new compressor and regas ,professionally fitted for $660 AUD. Very cheap indeed. Brand new compressor, genuine LG part $220.
timandsarah, The ECB in the picture is a cheap swap out! That looks exactly like the board i replaced for $48. The AC service place i go to looks on the LG internet site for dealers only ,enters the model and a exploded parts diagram comes up with prices.Can you test the dual cap yourself?

With a meter using the capacitance setting or a tester designed for that expressed purpose called a Cappy. HVAC techs have it in their meters MOST meters. Then each side is tested from each post to the shell for a ground out...should be open. The mfd for each side is written on the shell of the cap... there is A common post, a post that says herm and another that says fan.