My central A/C started acting up today. The thermostat is set at 75
degrees, yet the room temperature remains constant at 80 degrees. The
air circulating fan in the basement is running and putting out a
minimal amount of cold air, but the main RUUD heat pump/
airconditioning unit outside is just sitting there, not turning on. I
checked the circuit breakers and none has tripped.

I would appreciate some pointers on where to look for possible causes
before I call the repairman.

Thanks.