During planned heating maintenance it was discovered that the high temp limit switch was disengaging before the rated temperature (cut out at 136degf). In addition to this the flue gas deflector was missing. Both of these items were sourced, picked up and installed. The heating temps were rechecked and the system was operated until the return temp reached 78degf with no more intermittent interruptions due to the high limit switch cutting out early. The new wind guard was installed today. Thank you, Jon