I have a Rheem Model # RRKA-A024JK06E, it is only 10 years old and for 2 days now, I can not get the heat to come on longer than 30 seconds. It looks like a dual unit. Electirc for Air and maybe a pump for the gas. I can turn it on manually by connecting the red and white wires from the thermostat, but still only runs 30 seconds and doesn't come back on. Fan works, but only is blowing cold air. Talked to honeywell said was not the thermostat. Talked to a HVAC friend today, and said it could be a safety switch. Does any one have any ideas?