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?

[addiscott]

Flame gets sloppy almost immediately

[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?

[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.

[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.

[2sac]

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.

The supply house is, just that, a supply house. When I go to supply houses I always hear the guys behind the counter trying to help diagnose stuff over the phone. Their job is to take numbers you give them and turn them into parts, not diagnose your service call. Don't believe me? Call Grainger sometime and ask for technical help It's like talking to a barrel of monkeys. Do you have a senior tech to ask questions to?

[carmon]

The supply house is, just that, a supply house. When I go to supply houses I always hear the guys behind the counter trying to help diagnose stuff over the phone. Their job is to take numbers you give them and turn them into parts, not diagnose your service call. Don't believe me? Call Grainger sometime and ask for technical help It's like talking to a barrel of monkeys. Do you have a senior tech to ask questions to?

very well said..... go to the suppliers with earplugs...... they no almost zero on the service end....all the good ones are long dead......

[2sac]

very well said..... go to the suppliers with earplugs...... they no almost zero on the service end....all the good ones are long dead......

We've got a coupleof real good motor guys at some local motor supply houses but that's about it.

[Branderson0515]

If you are working on a G26 and the pilot is fluttering before main ignition, make sure you have the rubber gasket on the bottom of the fire box that the pilot tubing goes thru is installed correctly. I have seen air gaps in thst gasket cause pilots to flutter enough on ignition to cause flame rectification problems.

[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.

[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.

[addiscott]

thanks to all who tried to help. thanks to others for proving all trades have guy's who just have to piss into the wind.
I have solved the problem.

[pcp]

If you don't know how to test a flame sensor you should demand a full refund for your tuition.

[air1]

If you don't know how to test a flame sensor you should demand a full refund for your tuition.

That's a little harsh pcp.