I have a Carrier furnace Model# 58GS100-GB Series 160. Approximately three times within a 24 hour period, the calls for heat both during day & overnight (always once), the furnace will not respond to the call for heat, I am using the Honeywell digital round thermostat. The temporary solution to restore operation is to manually switch the thermostat from the heat position to off and back to heat. Thereafter, it continues to function properly until some time during the day. I immediately thought it may have been the high limit switch, however I shorted the contacts together overnight to test with alligator clips and the furnace still failed to respond to a call for heat. I have measured the low voltage transformer output at the thermostat to show approximately 28 volts, perhaps it's becoming weak? Assistance would be very much appreciated!