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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8429
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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8 year old York furnace shuts off after about 5 minutes. We

Customer Question

8 year old York furnace shuts off after about 5 minutes. We replaced the main filter, Repairman replaced the heat sensor and the board and it still shuts off. He checked the gas flow with a meter and it was fine. He said he did not know what else to do. he put the original board back since the new one did not fix it. The furnace runs great for 5 or less minutes then starts shuting off and going through the restart process. The furnace serial # XXXXX XXXXX Flame shuts off and then one flash, it restarts and flashed once again. It does this through all 5 attempts to refire then goes to eight flash code error.
Submitted: 6 years ago.
Category: HVAC
Expert:  Phil replied 6 years ago.

Phil :

Hi,This is risky business, not responsible for damages on your end. We keep going until you're satisfied. I come and go. be patient.

Phil :

Its showing signs of two defects but its probably just one... a failed flame sensor..

Phil :

try this first, find a long rod (flame sensor) poking into the pilot or main burner flame and sand it off .. get back to me with how that worked.

Phil :

We can go from there.

Phil :

Phil

Customer :

replaced it with no luck helping the problem

Phil :

The flame sensor operates by bleeding half its 24volt power supply to ground *through* the flame to the pilot light metal.. if the gas pressure is a bit high the pilot flame will not touch the pilot light shround and cause the flame sensor not to work.

Phil :

Look that over for me.

Phil :

If its not that we can look at the following in this orderr:

Phil :

The fact that this sudden restart you mention does not require a reset (such as after it shuts down after 5 tries).. indicates a problem with the electronics, or with loose connections.

Phil :

Try this, unplug and replug all the gang connectors and connections to the control card.. and see if that changes anything.

Phil :

I will be thinking about what the 5 minute aspect of the shut down might be abour.. it could be a condensate trap issue.

Phil :

Does this unit have a 2" plastic exhaust or a 4" metal one

Phil :

We can go from there, Phil

Customer :

Sorry for the delay...just got back! Ok...I am not certain what the pilot light shround is or what I should be looking at exactly...we have a 4 inch metal exhaust.

Phil :

Thanks.. find the main gas valve in the furnace by following the gas line, its a square valve with wires attached

Phil :

a pencil size aluminum tube is attached to that valve. thats for the pilot light.. follow that tube, on the end of it is the pilot light, with a tin thing on it that deflects the flame (shroud).. tweek that if necessary to the flame blows hard and strong onto the main burners. Next to the pilot, and in the pilot flame is the thermocouple flame sensor.. sand that clean if you want.

Phil :

Get back to me, Phil