I realized after re-reading the above that it wasnt very clear.
The boiler is a Utica MGB100HID, gas. It has a Honeywell gas control valve, and a Honeywell L8148E aquastat relay. So far, the only item that has been replaced is the Field Control damper motor assembly.
I had heard from a few people that the Field Controls gas vent damper frequently had issues. In this instance, when I moved the shaft slightly, the old damper would then rotate to the open position. Initially, just doing this would be sufficient to get the boiler to ignite. So, I picked up a new GVD-6 at a local supply for under $80 and swapped it out thinking I had solved my problem. Upon installing it, the behavior was the same essentially. Though right off the bat when i power cycled the boiler, the damper opened on its own, but it didnt fire the boiler. I made a phone call or two thinking I had maybe gotten a bad damper. I was told to try the following:
- disconnect wires from thermostat terminals
- remove Molex from damper assembly and test voltage on brown/black for 24 volts - checked fine
- reconnect wires from thermostat terminals
- test voltage on black/orange wires for 24 volts - checked fine
- using jumper wire, jump across orange/yellow wires in Molex (with damper in open position) to attempt to bypass damper - failed, boiler did not ignite with thermostats open and calling for heat.
I then traced Molex to Honeywell aquastat relay, opened relax box, removed cover. Disconnected Molex from relay and re-inserted, heard click, boiler fired. This has not been successful upon repeating! After a series of hours, boiler cycles off and the same problem persists even with damper in manual / open position.
This boiler does not appear to have a reset switch. if it does, I cant find it. On the manual /diagram, it shows a reset button on or close to the gas control valve knob. On mine, no such reset button.
I dont know enough about aquastat relays to begin to guess what else might be the issue, but I think my aquastat relay is doing what it should; ive seen the boiler serve zones with hot water without igniting the boiler when the temp was high enough. I just cant find any consistent behavior between the damper opening and the ignition firing by doing any of the steps Ive been doing.