It sounds to me like whoever did the compressor install did not do the job properly, there are many things that could go wrong when installing a compressor, everything must be done perfectly for the compressor to perform properly, if moisture was introduced to the system at the time of the compressor install and it was not evacuated properly this could hinder the flow of freon, if the unit was not charged properly it could not have enough freon or too much freon, my guess is that the warranty service that did the installation does not want anyone having a look at the pressures on the unit because they know it was a botched job in the first place, there is nothing to installing a bullet piercing valve and putting a set of gauges on the system to check the pressures on the system, any reputable company could do this is no time and you would know for sure what was going on. Although using a piercing valve is not really recommended as it could produce a leak later on, but at least you would know for a fact what the issue was. My suggestion is for you to call around to find another company in your area that does warranty work for LG and have them come out and repair the system properly. There are usually several companies in any given area that do warranty work for LG such as sears. Just call around to all the local appliance repair companies and ask them if they do warranty for LG and once you find one have them come out, they can submit the claim to LG themselves, there is no need to bound by to one company for your LG service.
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