If a thermal coupler is bad and the furnace is coming on loud upon the startup of the flame, can it also produce carbon dust buildup?

If a thermal couple is bad, the pilot will not stay lit, and the main burners will never come on. Your carbon buildup is caused by incomplete combustion, which can be cuased by many, many things.

My thermal couple keeps getting carbon build up why?

What can be the cause of carbon build up on a thermal couple

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Originally Posted by rowe2

if a thermal coupler is bad and the furnace is coming on loud upon the startup of the flame, can it also produce carbon dust buildup?

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sounds like delayed ignition of burners and not a thermocouple problem. Either you have a weak pilot flame or burners need cleaning--gas pressures could be a factor

. Yes carbonmonoxide could be discharged from furnace combustion area at the burners this should be looked at by hvac tech.

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Originally Posted by kel86

What can be the cause of carbon build up on a thermal couple

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Your pilot burner needs cleaning or adjusting. Pilot flame should be blue. If flame is orange--white this is an indication that pilot needs attention. Poor pilot flame causes the build up of carbon products on the thermocoupling.

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Originally Posted by Frank Mangrum

sounds like delayed ignition of burners and not a thermocouple problem. Either you have a weak pilot flame or burners need cleaning--gas pressures could be a factor

. Yes carbonmonoxide could be discharged from furnace combustion area at the burners this should be looked at by hvac tech.

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Your combustion chamber may also need cleaning as well as the secondary heat exchanger if carbon particals or soot is what you are seeing. The particles could be rust from inside of heat exchanger which were dislarged during burner misfire.