Old 05-26-10, 03:30 PM
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I installed a new LG window AC that's not cooling well.
On the inside side of the unit there's a lot of frost on the
evaporator fins, and I'm suspecting that's hampering the
airflow thru the evaporator, thus less cooling (In fact the
manual suggests this, but doesn't provide much help in
how to resolve).

I note there's a wire and something that looks like a
thermocouple (?) attached to the front of the evaporator, and
the frosting is up to the location of the thermocouple, with
no frosting on the remainder of the evaporator. I tried moving
the thermocouple away from the evaporator, the frosting stops, and the cooling seems much better.

Can someone tell me what is the function of the thermocouple (or whatever it is), why it would cause the frosting, and whether it's a good idea to move it away from the evaporator?

Thx, Gus
Old 05-27-10, 08:20 AM
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Not a PRO, but know a bit. The 'thermocouple' should be attached to a valve. The valve (a thermostatic expansion valve or TXV) should be bonded/clamped to the smaller refrigeration line attached to the compressor.

It's function is to control the flow of refrigerant through the coil so that the proper temperature/pressure relationships can be maintained.

Here's a link: what a typical TXV looks like.
txv - Google Search

The fact that you moved the sensing line may indicate that a clamp is missing. Look inside the case. I'm sure a PRO will be along to give more information.
Old 05-27-10, 09:44 AM
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The "thermocouple" could also be the sensing capillary for the thermostatic switch. Sometimes evaporator coils will freeze up in humid weather if the fan speed is set too low. Also, a low refrigerant charge might cause coil freezing. Since its a new unit, if it continues to act up, I'd return it or ask to have it checked by an authorized servicer.
Old 05-27-10, 04:27 PM
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On the LG window-banger what you are referring to as a "thermocouple" is the unit's thermostat. I suspect that you are seeing frosting of the evaporator because you have a high humidity AND are running the fan on a lower speed. Try running the fan on the highest speed and see if this cures the icing problem.

If it still ices then it is indicative of a low refrigerant charge and the unit should be replaced under the warranty.

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