LG code C6

Hi all. I know - it's an LG! A12AWD, AS-W12PDGO, SP1 chassis. One of those 'Art Cool' interior units.
Called to unit which according to client is 'short of gas'. Absolute crap install, but the end result is error code C6. Excessive current at inverter.
Compressor does not run at all, but fan motor does. Fan motor runs for less than 1 minute and shuts down. This is repeated 4 times, and interior unit displays C6 and total unit shutdown. Disconnect compressor and the sequence is the same.
Resistances at compressor windings within the LG range of between 1 and 5 ohms each.
Yellow - Blue 2.5ohms,
Yellow - Red 2.7ohms,
Blue - Red 2.9ohms
I wouldn't have thought that the difference in resistances significant.

I've removed the PCB and have just kicked under my desk until I've some clue as to where the fault lies!

Any ideas??
Graham

I would check if the compressor is down to earth and also if the output from the inverter is OK.

:cool:

Hi Graham,

This little nugget should help.

http://www.refrigeration-engineer.co...verter+testing

http://www.refrigeration-engineer.co...attach/pdf.gifAndy's Inverter Testing Guide.pdf
this is handy too- pity theres no mobile number for techy help!!!

Top man! Gonna have to dob you on the commission.

Got this number for LG but not sure if it still works: 0870 8720791 option 4

Quote:

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Originally Posted by install monkey

http://www.refrigeration-engineer.co...attach/pdf.gifAndy's Inverter Testing Guide.pdf
this is handy too- pity theres no mobile number for techy help!!!

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Thanks for your replies.
Forgot to add that I had already meggered the compressor and appears ok. Didn't get any output on compressor connector during the time the fan was running.
I'm tending to think it's the board, but will run through Andy's test guide.
Not too sure where to get LG parts here - could be interesting!!
Thanks, Graham

Next....
Once again, thanks Andy for the test guide.
This has just got to be a LG thing - there are no terminals marked P and/or N! I guess that these measurements to be taken are within the SPM circuitry, not the Power Module.
There is a lot of soldered joints on the board that appear corroded/dull/dry. I'll photo and post when I have time.
Any other constructive comments welcomed - Hmmmm, I think!
Graham

http://www.mediafire.com/download/dn...erter_test.pdf
http://www.mediafire.com/download/k1...viceManual.pdf
these links any good??

Thanks IM. They have helped a little. I'm not a stranger to electronics, but would like to clear a couple of things in my head. (commonly known as the space between my ears -- I'll say it first!!)
I've sorted many non-inverter PCB problems, both interior and exterior, but this my first inverter problem. Maybe I've been lucky!
Are the P and N terminals that Andy refers to, the DC side of the rectifier bridges? And - is 320Vac normal at these terminals. I do not have P and N terminals as such on this LG board, but can easily get to the diode bridge joints.
Am I right in assuming that the voltage at compressor will be AC? If so, then the SPM is the actual inverter module for compressor control. What are the variables at compressor - voltage, frequency, or a combination of both?
Once again, thanks for the info guys.
Graham

Quote:

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Originally Posted by aircon50

Are the P and N terminals that Andy refers to, the DC side of the rectifier bridges?
Yep

And - is 320Vac normal at these terminals.
Nope. It's then output of the rectifier so around 320V DC for a single phase rectifier or 540V DC for a 3 phase one.

I do not have P and N terminals as such on this LG board, but can easily get to the diode bridge joints.
Should be good enough for testing unless something has gone wrong between the diode bridge and IPM.
Look for the inverter module on the PCB. See if you can follow the compressor wires to help locate it. compressor connections U, V and W are on one side of the chip, above is P and below are 3 N terminals which are all connected together. Page 54 of the manual in IM's post shows the PCB layout. Look at the top picture then the inverter chip is in the bottom left. P on top, then U, V and W and the 3 N's below.


Am I right in assuming that the voltage at compressor will be AC?
Yes - a 3 phase output but actually made up of loads of square waves.

If so, then the SPM is the actual inverter module for compressor control.
Yes, SPM2 on the circuit diagram.

What are the variables at compressor - voltage, frequency, or a combination of both?
Frequency is the variable but your meter will show an average voltage value which will change with the frequency. As time has moved on now some units altered the value of the highest value of the square wave (PAM control - dunno how but would like to know...) then pure sine wave outputs (as plastered on the sales guff) instead but for testing purposes they are all checked the same.

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That's about my limit of inverter theory. The inner theory behind the development of these inverters still gets me a bit curfuzzled and I've just scratched the surface, read stuff about vector control which made no sense. Still trying to suss out what superheat is...


Spanks!

Thanks. I've just re-read my questions and realised I put 320Vac when I should have put Vdc.
I'm hoping to go back Monday or Tuesday to recheck. I'll update as and when!!
Superheat - I've heard the expression! Or is that what we are having today? Forecast of 32ºC +!
Graham

http://www.eetasia.com/ARTICLES/1999...URCES=DOWNLOAD
http://youtu.be/9z7ftykzoA0

Thanks IM. The article should make interesting reading.
Have now confirmed that the fault is with the exterior PCB. Rechecked compressor windings resistance and insulation. Managed to get a DC reading at rectifiers of 290Vdc, but nothing at compressor connector.
Client is going to have a complete new unit (not LG, I hasten to add!).
Now I've got to go to their shop and sort out an old Season unit.
Once again, thanks for your assistance.
Graham