Window unit 5000++ BTU

[joerocket]

Hi All

I have this small LG 12000 BTU window unit which totally stopped working. Power from wall socket is good. Power plug and wires good.

Opened the unit up and saw the wires going into the 'Common' pin of the 2-in-1 capacitor, fried. I repaired all the wires/pins and also checked the dual capacitor for (Herm)30uF and (Fan)5uF. Both show me what they supposed to show. Fixed up everything and bingo, the unit ran. The compressor kicked in but stopped about 2 seconds later!!. after 60 seconds, it ran again and 2 secs later it stopped. that is how it was all the way.

From my findings, the high temp switch located on top of the compressor could have opened the supply to the compressor since the compressor gets too hot. So what could be the problem?

Capacitor capacitance measured, ok. But one thing i dont understand is, this compressor only has a run (herm) capacitor (2-in-1 capacitor with the other lead for fan). Why does it not require a start capacitor?

Any kind of advice is much appreciated

[install monkey]

psc- permanant split capacitor
clip the current when its trying to start- if it buzzes its probably siezed
unplug the 3 leads to the compressor and test resistance accross the 3 pins, you should have 3 resistances of different values this proves the windings are ok

[joerocket]

compressor windings are good from c to s, c to r and r to s. All have readings. BW the compressor capacitor is a run or start cap?

[install monkey]

http://www.hvacrinfo.com/Tecumseh_bulletins/compressor.pdf
click on the link - page 3
its both its wired between the windings

[nike123]

Highly possible seized compressor! Before you change it, you could try to change to new (from the shelf) capacitor (that is permanent run capacitor) because measuring capacitance of that capacitor without load, only with universal instrument and with 25 times less voltage will not tell you anything about his capacity at full starting current (5-7 times higher than normal running current) and working voltage of 220V.

If capacitor is not up to the job, motor of compressor cannot overcome inertia and pressure resistance building in compressor and motor stalls. Stalling motor pulls to much current and that trigger over-current/over-temperature relay which is in series with common lead of compressor. In 2 seconds, compressor does not have time to heat its head enough to trigger over-temperature part of relay, therefore it must be connected with over-current problem.

If motor is not seized, and enough time is passed between two start to pressure equalize in system, then problem must be in bad capacitor or faulty over-current part of relay.

If change of capacitor doesn't help, than it is possible to check over-current relay is faulty by starting compressor with bypassing over current relay, but that is something which should be done by skillful and experienced technician, and not amateur, since burning of compressor windings and contamination of system is very likely, if not done with monitoring current and fast hand on switch, which will make service of that unit uneconomical.