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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7582
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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El heat air unit natural gas. Flame won,t stay lit blower

Customer Question

Hiel heat air unit natural gas. Flame won,t stay lit blower continues to run. Flame sensor replaced board showed sensor fault again. Tech said had same problem recommended replacing both boards. Worked fine for maybe 4 hours then back to same thing.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, you will need a multi meter with a Micro Farad scale on it to measure the current flow from the end of the flame sensor wire to the printed circuit card where it attaches.

Expert:  Phil replied 1 year ago.

ooops... Micro Amps. Not micro farad

Expert:  Phil replied 1 year ago.

We will be looking for 2 to 5 micro amps.

If you have that current flow from the flame sensor wire to the card and are still getting a flame failure error, then the printed circuit card is most likely bad.

Expert:  Phil replied 1 year ago.

If you do not get a 2 to 5 micro amp current flow to the card, then it could be the fault of the card or the a bad ground in the flame sensor circuit...in that case a 'flame simulator' is needed if you want to prove the card is bad or not. $45 made by Johnson Controls.

Expert:  Phil replied 1 year ago.

It puts a simulated 5 micro amp signal to the card, if the no flame error continues then the card is bad for sure.

If the furnace now works, then there is a faulty ground at the burner head, due to rust on the burners or a problem with the furnace grounding.

Expert:  Phil replied 1 year ago.

Thanks for letting me work with you. When we are finished,if my answer has been polite, professional, and thorough, please locate the 'rate your expert button' and click one of the ratings .I fyou still need help let me know!. Rating will not increase your charges, nor close the question, but is how I earn my living. Thanks again.