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· Registered
23 Posts
Discussion Starter · #1 ·
Hi all, I'm looking to hear of anyone out there is familiar with this specific problem -

The issue:
4-year old 3-zone hot water baseboard Utica Boiler stopped firing last week. Thermostats seem to work, circulator pump runs and can hear the click of the thermostats when a call is made for heat on each zone. The Field Control GVD-6 damper, when set to automatic, doesnt open. I can get it to open (occasionally) by moderately wiggling the damper shaft or by switching it from auto to manual and back. this DID result in my boiler firing for the last two days, producing heat. A relative who works for a local gas utility that does repairs asked me what type of damper I had and I told him the model of the Field Control and he was the one who suggested wiggling the damper shaft. Once open, i left the damper on manual. However, subsequent calls for heat would not ignite the boiler.

I replaced the GVD-6 with a new one, at my relative's suggestion. As soon as I installed it, the behavior was the same. I can occasionally get lucky, and the GVD-6 will open, and then I will hear the boiler ignition kick in. However, it is not consistent.

To further troubleshoot, I followed the Effikal damper troubleshooting steps and jumped the yellow/orange wires on the Molex to the damper - with the damper open, and it will not fire my boiler to ignite.

I managed to get it to work just now by unplugging the molex from the damper from the Aquastat relay, and replugging it in. I heard a 'click' and then the boiler fired.

So my questions:
- Is my damper indeed good, or bad?
- Could it be the aquastat relay?
- Is it a thermocoupler or something with the ignition?

Ive had two days now where once I can get the damper in the open position (set on manual) and i manage to get the boiler to ignite, I will have heat for some period of time until it will not cycle on again. Other thing of interest: I heard a fairly low grumble/rumble yesterday when the heat was going on prior to the sound of ignition. I was upstairs and not next to the boiler when it happened, but i felt the vibration in the floor and it definitely was not a 'normal' sound that Im used to after 4 years in the house. I was thinking this might be a zone valve?? I dont know much about HVAC only what Ive been reading online and learning as I go.

Thanks for any insight!


· Registered
23 Posts
Discussion Starter · #4 · (Edited)
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.


· In Loving Memory
42,671 Posts
Turn up thermostat. Aquastat should send power to damper if boiler water temp is below aquastat setting.
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