I am having a repetitive problem with my upstairs A/C unit. It is a ~12 yr old York HLRA048S06D 4-ton 10 seer (?) unit. When it works, it blows crisp cool air in the 100+ temps we've been having here in TX. When it doesn't, the interior fan continues to turn on when needed, but the outside condenser unit does not turn on, and the upstairs does not cool. For the last week, it seemed to be limited to nighttime when it shut off, but this weekend, it was off for long periods during the day as well, turning back on randomly. I noticed this weekend as well, in the mornings when I turned it on manually to check, the fan was not spinning and there was a buzzing sound coming from the unit. I left it on, with the interior fan blowing and the condenser not on. Later on though, it started to cool once again.
I had an A/C technician come out to check on it in the afternoon, but by the time he came, it started working again, and as it was blowing cold air he could not diagnose anything wrong. The condenser fan spins freely, no breakers are tripped. He didn't go upstairs into the attic to check on the furnace, was there anything else he should have done? Am I able to bring in a technician again even though it's random when it goes on or off?