I was working on a 2 ton York heat pump, cased evaporator coil with gas heat today. It had a bad schader valve and was low on charge. I evacuated the unit, pressure tested, to look for other leaks and put 5 lbs of R-22 back in.

While charging the unit I noticed control panel red light in the condensing unit was flashing 4 times. Unfortunately there was no info on the unit(surprise) which would tell me what the 4 flashes meant. I haven't worked on many Yorks so I've got no clue what the code is. It looks to be about 10 yrs old, again no nameplate info could be found.

Also the unit didn't have any pressure switches. After charging the unit the low pressure side was still low. I suspect a dirty coil since there were no air filters installed on the unit. I didn't want to keep pumping refrigerant in plus it worked fine in heat mode. I didn't have time to inspect the coil since the customer didn't want to pay overtime. So, I've got to go back Monday to finish the job.

So back to my orginal question, does anyone know what the 4 flashes mean? And what else might cause a low suction and head pressure. Outdoor temp was about 75 and indoors it was 80.