I have a heat pump outside and a blower in the attic. Both made by YORK. My system stopped cooling a week ago. The blower keeps running but the heat pump does not start.

I checked the circuit breaker in the basement and the power disconnect next to the outdoor unit. Both are good.

I studied the manual it says on cooling calls, the system makes a R to O to reverse the heat pump, a R to Y to energize the contacts which starts compressor and fan, a R to G to start the blower. I removed the cover from the control panel of the heat pump. There were no visible loose wires. I tried a power detector like a screw driver and it detected power on incoming contacts. I watched when the blower started, a small metal plate on the contacts block closed. Then there was a noise that lasted about a second. Both the compressor and fan did not start. The noise repeated about every minutes.

Currently I have the system in "OFF".

What should I do from here?

Thanks, RB