Found unit in continuous spark due to sensor not reading standing pilot. Cleaned ignitor sensor which corrected issue. Further found ignition module not sending voltage to main gas valve (MV) during call for heat. Diagnosed bad ignition module. Credited previously charged amount for relay switch. Billed as service callback. Will have to order ignition control module and reschedule repair. 1/21/20 Returned and replaced ignition control module. Replaced transformer and installed in-line low voltage fuse. Found and replaced shorted thermostat. Cycled system in heat. Verified proper limit winding and blower operation. Tested t-stat operations. Everything is operating normally at this time.