I have been working on a York Liquid Chiller M#YCAZ33BA3-46PA S#RKEM6953AA. I have a system fault of "Motor Current". I have (2) O6Z's reciprocating compressors 6 cylinder type. Both compressors are not original and have been replaced at one time or another. I went to the trouble shooting section of the operations manual and they suggest (3) different things will cause this alarm. Bad relay output board, bad motor protection device and faulty high pressure switch. The relay output board was replaced about a year ago. I checked my high pressure switch and is working correctly. I swapped out the motor protection between compressors and still had a system fault on Circuit (2) which disables Circuit 2 compressor. The tests I have done till now are as follows: Performed acid test on Circuit (2) compressor. Megged out the condenser fan motors. Both came back satisfactory. My next step is going to get oil sample to send over to a lab and get analyzed. Any other suggestions would be appreciated.