Troubleshooting an oil issue today... On start up, the it had 50 psi oil pressure difference, the control is preset for a minimumof 9 psi. The oil sight glass looked a little low, I can make the guess that when the compressor unloads 2 heads, the oil return drops off and we lose our oil differential. It's been left off until we can get some oil in there. Testo North America Sealed Unit Parts Co., Inc. #hvac #hvacr #refrigeration #commercialhvac #hvacsystem #hvacaf #hvacbusiness #oilfailurecontro