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I have a PAH90AF and it will not Ignite. The Igniter is

Customer Question
I have a PAH90AF...

I have a PAH90AF and it will not Ignite. The Igniter is sparking and to pilot is lit. The flame came on once when i heard a click and then went out. The power vent is running and the big fan is also running. I was thinking pressure switch but it is trying to ignite but seems lack of fuel or valve opening. Nay suggestions ?

Contractor's Assistant: I'll do all I can to help. How long have you been dealing with this?

Well the furnace hasn't run in some time because of this conditio. So yesterday went through and clean and check all fuel lines, exhaust and wire conections

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

Yes except the fuel valve. not sure if there is one in there as there are safety torx on the cover

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

Yes

Submitted: 6 months ago.Category: HVAC
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Answered in 6 minutes by:
1/9/2018
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 9,693
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Verified

Hello, if the burner ignites for a second or two then goes out, the cause is almost always a dirty flame sensor rod. You can clean that off with steel wool.

.

That would be the first step, it has about an 70% chance of working... there is a 30% chance the printed circuit board is bad, I am estimating that based on the main blower running when the burners are not on.

.

If you want up to 24 hours of coaching well above 'Just an Answer' rate positively now, then

Take close up, exceedingly well focused photo's of the wiring diagram glued inside the furnace/air handler door, and the printed circuit board mounted on the blower, , that shows where the thermostat wires connect, and I will mark them up with trouble shooting instructions.

Use the 'add files' link next to your send button to get the photo(s) to me.

.

We can go from there with training, coaching and diagnosis.... without a time limit, In depth with as much detail as needed .

. select the 'finish and rate your expert link' near the top of your page and click on it.

.
My goal is to give you the best experience possible! I hope I have earned a 5 star rating! Please remember to rate my service by selecting the 5 stars at the top of the screen before you leave today. If you need more assistance, please use the reply box and let me know.

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Customer reply replied 6 months ago
Where would i fine the flame sensor rod on this unit?
HVAC Technician: Phil, Mechanical Engineer replied 6 months ago

The flame sensor rod will be poking into the burner flames on one of the burners, about an inch above the burner... all you will see is a small white ceramic piece with ONE wire coming out and running to the printed circuit board... its held in place by a 1/4" hexagonal head screw, remove the screw and pull the flame sensor out to clean it..

.

click here please, this should be close to the model you have, see page 24 for flame sensing circuit

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