My son, who lives in LA, has a problem with his AC which occurs during the hottest part of the year. The unit is a Lennox package unit installed on his roof about one year ago. During the hottest part of the summer (90's), before the set temperature is reached, the unit would shut down and it would say "waiting" on the thermostat for a period of time.. Although the HVAC contractor is responsive, he can not seem to solve the problem. Any help would be appreciated.