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Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21780
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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Boiler Model 234-5PN Series 'C' Lights; then goes out in

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Bryant Boiler Model 234-5PN Series 'C' Lights; then goes out in about 2 - 5 seconds. Then will relight again. Pilot stays lit. Heavy soot. Same problem with chimney pipe removed.
JA: How long has this been going on? And how severe is the problem?
Customer: Report of no heat yesterday.
JA: Do you plan on doing the work yourself?
Customer: Sure. If practical & safe. Looks like it needs a good cleaning and a switch or 2
JA: Anything else we should know to help you best?
Customer: I think that is it. I have no wiring diagrams or I'd be further along.
Customer: replied 8 months ago.
Gas control valve is Honeywell VR8304M4507.
It has 3 wires leading to it. From thermacouple through the water temp mercury switch, then the 3rd wire connects to an unknown wire that leads into the boiler insulated area, this wire has 2 leads but only one is connected to the Honeywell wiring mess. The 2nd wire looks unused and is in the free air.
Disconnect any of the 3 wires from the Honeywell valve and it will not open to flow gas to the burner, even for the few seconds.
When operating with all wires connected as original, I can hear the valve chatter to open. Valve is quiet when no gas flows.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Sounds like your boiler needs to be cleaned. It sounds like it's clogged with soot which is an indication of inadequate air for combustion. You also need to address the combustion air issue or this will happens again.

Customer: replied 8 months ago.
I'll get it cleaned up and let you know if problem is solved or if further detective work is needed.

You're welcome. You also have to address the combustion air problem

Customer: replied 8 months ago.
Yep. Cleaning will include chimney.
There must be an O2 sensor or an air flow sensor somewhere. I don't see that in the wiring diagram I finally found.

Flame is probably rolling out and tripping the rollout sensor or the heat diverted because of the soot is tripping it.

Rick and other HVAC Specialists are ready to help you
Customer: replied 8 months ago.
Very accurate answer. Problem solved. I did hire a professional to do the work since I felt the answer lacked the background information that a non professional might need to complete the cleaning and possible needed repair in a safe manner.
2 of the 3 repair estimates agreed with the Rick's general assessment and that gave me the piece of mind to OK the work.