Carrier 58SS Issues
Symptoms: Thermo calls for heat; inducer fan comes on; pilot lights; approx 60 sec burner lights; burner goes out in 4-6 sec (pilot stays lit); burner relights in approx 6-10 sec; sequence repeats; burner stays lit on relight 7th or 8th time; circulating fan starts approx 60-80 sec; sometimes during heat cycle the burner will go out, and instantly relight (circulating and inducer fans uninterrupted).
I have replaced the 3 wire pilot assembly, the lower control board, the pressure switch, and the inducer fan control board (relay contacts were burnt) and the symptoms persist. I have cut all power to the unit several times to see if timers would reset, to no avail.
In checking voltage to the gas valve, with R&W jumpered to bypass the thermostat, I note 24 VAC to gas valve term #4 and 0 VAC at term #1 (initially); after several seconds (while the inducer fan is running) 24 VAC is applied to term #1 and shortly thereafter the burners light. A few seconds after the burners light voltage disappears from term #1, burner goes out; and the same cycle repeats. After several such cycles 24 VAC does not disappear from term #1, burners light, fan starts and ops okay. Something is interrupting 24 VAC to the #1 term on the gas valve, apparently causing the burners to go out, once lighted -- but, cures itself after several cycles. ...???
Any help will be much appreciated.
Barney, in Memphis