Upon arrival both units were on but only lower floor was running. The upstairs unit was flashing the error code for communication error. With this unit an overflow switch was installed to interrupt the communication wire. Checked the drain pan and found there was a clog in the drain line and water was sitting in the unit’s drain pan. Blew out the drain line for both units and poured water into the drain pans to clear any remaining blockages. Also used a shop vac to suck out any possible clogs remaining. Turned power off to the unit to clear the error code and then started and tested the unit. Had good temps coming out. Unit is working properly