We live in a 70's home, with a gas heater, and the heat had been turning on (delayed) and then turned off inconsistently last winter. This winter, we would turn up the heat, and sometimes it would turn on and sometimes not. So, we replaced the heater thermostat with a LUX digital thermostat, and it turned on once, hours after we turned up the heat, and since has not turned on again. So, it doesn't appear that the termostat was the problem, but what could it be? Starting to get cold in Calif...