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My furnace turns on and shuts off after 5 seconds. I cleaned…

Customer Question
My furnace turns on...

My furnace turns on and shuts off after 5 seconds. I cleaned the flame sensor and then it would stay on for 30sec and give me a low sensor signal fault. I purchased a new sensor and its gone back to only staying lite for 5 seconds. No fault codes

Contractor's Assistant: Did you check the furnace's filters?

There does not appear to be any on this unit

Contractor's Assistant: Do you plan on doing the work yourself?

Yes. I can't afford a svc call

Contractor's Assistant: Anything else we should know to help you best?

Not that i can think of

Submitted: 7 months ago.Category: HVAC
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Answered in 1 day by:
11/27/2017
HVAC Technician: airheatman, HVAC Technician replied 7 months ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,213
Experience: Furnace, A/C and heat pump specialist.
Verified

If flame sensor is sending signal to the board, we either have a loose ground wire, a loose connection or a bad control board.

1.Make sure furnace has a proper hard wire ground(Not plugged into a rectacle)

2.Unplug wire from senser to board ,clean and make sure it is seated and making connection.

3.Install a digital meter (set to microamps) in series between flame sensor and board.See video below.

4.If we are getting at least 2.6 to 2.7 micro amps to board from flame senser, ground is good and connections are good.replace board

https://www.youtube.com/watch?v=a5u044OJBc4

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HVAC Technician: airheatman, HVAC Technician replied 7 months ago
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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,213
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