Came out to call, tenant stated that the heater was running constantly and not shutting off. We were out recently to fix another issue on the system. I checked the system over and found the heating elements activated and the thermostat not calling for it. I found the double stack sequencer had failed and was causing the heater and fan to run constantly. I replaced the sequencer and double checked system operation. Heater is no longer running constantly, and system is operating properly.