Found Walk-In Cooler compressor not running when I arrived, tested voltage to compressor and was good, compressor was trying to start but making a knocking noise when trying to start, tested compressor and found to be bad, compressor is on order at united reading and will be picked up today and someone will return to install. 11/27/19 Recovered charge from existing unit, removed compressor and filter drier. The old compressor was all braze in, new compressor is a roto lock. modified piping into new compressor. leak tested with nitrogen, pulled deep vacuum and put recovered 404a back into unit. unit went down to 34 degrees and cycled off.