flame sensor?

[addiscott]

First off I am fresh out of school so pretty green but would like a few opinions on a furnace I'm trying to get going for a friend.
Lennox 90% Furnace starts up normally but flames get sloppy within a few seconds then go out and starts over. the code says flame sensor but the flame on burner the sensor is on gets sloppy very fast and not sure sensor has time to heat up. I have cleaned it with brillo, same outcome and sensor looks really good. combustion air switch checks out good.

orderd new flame sensor so figured I would run by y'all while I wait.

Thank you for your time, Scott

[captube]

Clean the burners and crossovers and check gas pressure.

[air1]

Does the flame get sloppy when the fan comes on?

[snupytcb]

have you checked the air intake? you should not use a brillo to clean a flame sensor. use a bill. if the flames are getting sloppy i wouldn't think the flame sensor is at fault. what was the gas pressure?

[addiscott]

Flame gets sloppy almost immediately

[Joehvac25]

The flame sensor is the safety not the problem, what model?

[addiscott]

that is what I thought, G26Q3-75-6

[air1]

My guess is that you're not getting a good draw through the heat-exchanger. Either your inducer draft motor is not working right or you have a restriction in the combustion air path. Check your intake, exhaust and heat-exchanger. Could also be a breach in the heat-exchanger not allowing the inducer fan to create the necessary draw.

[Joehvac25]

that is what I thought, G26Q3-75-6

I've seen the secondary's plug on these and there under warranty. Pull the inducer and make sure the wheel is good and maybe the cover on the secondary side.

[syndicated]

I'll bet the secondary is plugged from years of poor drainage.
Pull the collector box and have a look.

[addiscott]

Thanks alot! As I said I'm a little new but I shouldn't have second guessed myself. This is the track i was taking but supply house said flame sensor.

[Joehvac25]

Thanks alot! As I said I'm a little new but I shouldn't have second guessed myself. This is the track i was taking but supply house said flame sensor.

Idiots!

[t527ed]

if the flames are sloppy right after ignition look for intake or exhaust restrictions.
if flames get sloppy when blower starts look for a big crack in the primary heat exchanger just inside of the burners.
early G26 furnaces had a burner alignment issue that let flame impinge on wall of heat exchanger, new HX comes with burner assembly that MUST be used.