Good Morning, I hope someone can help. I have a York 2 or 3 ton unit outside for my down stair that for some reason as of yesterday when I lower the thermastat nothing happens. When I shut the unit off in the house and restart it I here, I guess the fan motor start, but that is all. I have noticed that recently is has not been blowing the cooleset of air but that could be due to high ceilings and really hot climate. Unit is 6 years old never been serviced. I believe model number starts out like "York HRRA0505360"
Check AC circuit breaker. Listen to outside compressor/fan unit while having someone switch thermostat from off to cool. Both fan and compressor have to come on. The uninsulated coolant line will get warm if compressor functioning.