I have a YCAV207 that is starting both compressors at the same time,every time. The only recent problem I have had with this unit is a bad outside air temp sensor which has been replaced. I was at the job site on Friday and noticed it was starting wrong and cycling frequently. This chiller has standard IPLV and should only start one compressor at a time. It is also only in the 60's out side and I have very little load as it is at a church. I suspect the micro board or EPROM. Note - when I turn off either circuit with the system switchs they respond correctly. Any input is always appreciated.