# Lennox G50 series not igniting. Codes are alternating slow flashing.



## yuri (Nov 29, 2008)

That code is failure to light burners not a pressure switch code. When it goes to start does the igniter by the right burner glow red hot (looks like a thin black matchstick).


----------



## stik1964 (Jan 16, 2011)

I just got home and turned the power off to the furnace, took off the two doors a on the front, replaced them and the furnace fired up on its second attempt. The code from the lights is now low flame signal, check flame sensor, however the furnace continues to operate. I am willing to bet the furnace will not fire up after it heats the house up this time. I did not get a chance to see if the right burner glows red hot. I will check that soon. I did not notice it before when teh furnace was not igniting. The signal is slow and fast lights, not normal operation right now.


----------



## yuri (Nov 29, 2008)

Clean the flame sensor with fine emory paper AND the face of the burner it sits in front of. Left side burner. Looks like this:


----------



## stik1964 (Jan 16, 2011)

I will clean the sensor and the face of the burner it sits in front of. Just a note, after the thermostat got to temp, the furnace shut off and the lights are signalling slow alternating, which means watchguard, burners failes to ignite, limit open longer than 3 minutes, flame sense lost 5 times in one heating cycle. I will attempt the cleaning and tell you what happens. Thanks again.


----------



## stik1964 (Jan 16, 2011)

Last night since cleaning off the flame sensor and the face of the burner, the furnace has been working just as it should, and the led lights are flashing the normal operation mode. This has been happening now for over 12 hours. I am hoping that this is the solution, so far so good. Thank you so much for the assistance. I do have one more question. I have a separate furnace for my second level, and my daughter's and son's two rooms face the west. It is always too cold in the winter. The vents are clear and they get some air flow in there. The windows are covered with plastic.


----------



## yuri (Nov 29, 2008)

Pretty hard to tell w/o being there if there is enough heat going into those rooms.


----------



## stik1964 (Jan 16, 2011)

Thanks again for your advice. The furnace has now been nearly 24 hours with working without incidence. I am hoping that this is the fix. Is there any other things I can do as far as preventative maintenance. I am diligent with the filters. 
Thanks Again. Anything else I will let you know.


----------



## yuri (Nov 29, 2008)

Not really, but you should clean the sensor and burner once a year and try to keep the basement dry in the Summer with a dehumidifier if necessary. Moisture corrodes circuit boards and can shorten their life. Damp basements are bad for mold and other problems.


----------



## blastermaster (Jan 20, 2012)

I had the same issue and same error codes as described by STIK1964. I am glad I found this thread. I powered off the heater, removed the flame sensor, and cleaned it with emory paper. Put everything back together and powered on the heater. It's been through few cycles with no issues. 

Thanks everyone for your help. :thumbup:

FYI, if anyone need to replace the flame sensor, you can purchase it here:

http://www.furnacepartsoutlet.com/products.php?product=Lennox-52W29,-52W2901-Flame-Sensor.-G40,-G41,-G50,-G51,-G60,-G61-and-G71-furnaces.


----------



## stik1964 (Jan 16, 2011)

I'm back. Same furnace same issue. The right side does turn red but the furnace will not ignite. Have cleaned all and still will not fire up. What to do now?


----------



## how (Feb 26, 2011)

The next step after the igniter glows should be the gas valve opening up to allow the gas to be ignited on that igniter.

Do you have gas to any other appliances in your house? Stove/Hot water tank?
Is the furnace gas shut off ....open?
Is the gas valve toggle in the 'on' position?
Do you hear a solenoid click sound from within the gas valve when the igniter is glowing?
Do you hear any hiss of gas flowing into the burner compartment?
Is the gas valve receiving 24 Volts when the igniter is glowing?


----------



## yuri (Nov 29, 2008)

All of the above as How posted.

Low gas pressure, gas valve sticking closed and I get a few of them.

The igniter glows for 15 or more seconds to warm up B4 the gas valve opens. 30 seconds max.


----------



## stik1964 (Jan 16, 2011)

Yes, I here the clicks and the gas is hooked up to the water heater also. I do not here a hiss. It may be a gas issue. Gas on, solenoid clicks. Not sure what to do next. Igniter glows and turns off after alloted time. Several seconds. Will cycle 5 times and start flashing alternating.


----------



## stik1964 (Jan 16, 2011)

Also, I have 2 furnaces and the upstairs one works perfectly.


----------



## how (Feb 26, 2011)

Most likely the gas valve. Time to call a tech.


----------

