See the enclosed diagram, the oil temp control also known as the AMOT Valve. its main job is to bypass the oil cooler if the oil is below 110 I believe, This is done by an internal temp sensor that opens the port from the oil sump and closes port from outlet cooler side which will start the bypass. once the oil warms up it will close port on top side run of AMOT and open port on bottom side run which will then allow flow back trough cooler. As part of regular maintenance on the machines with AMOT it should be checked with temp gun to ensure its not sticking or in bypass when it should not be. Also the oil line to the top of compressor should be checked during running to see what temp you are feeding the compressor Hi speed. To cold and the oil will high refrigerant percentage and when it hits the hi peed it will foam and the heat removal/lubrication capability of the oil will be very low. I will look for more stuff but this a start