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Robert
Robert, RV Mechanic
Category: RV
Satisfied Customers: 12150
Experience:  18 yrs. RV experience including Cummins North West, Country Coach, Monaco Coach - vendor certified.
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Dear Technician, I am writing you from Houston TX. I own an

Customer Question

Dear Technician, Good Evening. I am writing you from Houston TX. I own an Atwood Furnace Mod. 7920-11 Sr.(###) ###-#### I removed a mud dobber's nest from the exhaust pipe. I may have caused some mud debris to fall back into the combustion chamber. A local Technician advised me to blow compressed air into the exhaust pipe to expel dust. When I tried to restart I got immediate ignition followed by a fast shutdown. The unit would reignite and shutdown for at lease six times.
On my own initiative I removed an aluminum plug from the gas delivery device just before the orifice and blew compressed air into the combustion chamber. Now when I try restart the blower comes on and the gas valves clicks open and again clicks shut. I receive an ignition Lookout Fault signal. Please advise a remedy. Thanks Richard
Submitted: 1 year ago.
Category: RV
Expert:  Robert replied 1 year ago.

Hi my name is Robert....

You say that after the blower comes on the gas valve clicks, at the same time the electrode should spark, is the electrode sparking at all?

Robert

Expert:  Robert replied 1 year ago.

Please keep in mind this might take some going back and forth, follow ups are included and so far I need more information to go on....

Robert

Customer: replied 1 year ago.
Robert The electrode or glow plug is not sparking or glowing. However I got ignition from the electrode or glow plug before I removed the Mud-dobber's mud nest. The furnace gives me a signal of 3 Flashes with a 3 Second Pause. and Atwood's booklet calls this signal an "Ignition Lockout Fault". Could my use of compressed air cause some damage to the electrode or the glow plug?
Expert:  Robert replied 1 year ago.

OK

The key is the no spark, the same time the gas valve opens it should spark, if it is not sparking there is an issue with the electrode or circuit board.

So I would have the board tested to start. Most RV shops have a special board tester and can tell if the board is bad. IF the board is good and it is not sparking I would replace the electrode. I would also try and have the LP pressure checked at the back of the furnace, a manometer is needed for that. IF it was sparking and lighting off then it could be a LP pressure issue, it is going to be a process of elimination, click HERE for a service manual, it will show you how to test everything.

Also the mud dauber issue is a concern, sometimes it is very difficult to get all that out without flushing with water. That would require the furnace to be removed. I have seen some real bad ones where air alone did not help....

IF you need more help please let me know.... Robert

Expert:  Robert replied 1 year ago.

Hi.... Was just checking in to see if my answer helped, if you have more questions or concerns please feel free to contact me... Robert