Lennox furnace - Bad flame sensor - Will DIY Invalidate warranty?

[K_W]

You can unplug them and jumper the wires. Do one at a time.

I will try that in the morning. I don't think they're being tripped by a flame problem because the metal around them doesn't even get warm to the touch before the gas gets shut off.

 

[sljccj]

Im pretty sure there will be more than those 2.

 

[K_W]

Im pretty sure there will be more than those 2.

I'll look but I only saw those two, the flame sensor, and the vacuum sensor pretty simple furnace.

 

[BGDave]

If you ever get in a bind for parts there is always Shortys HVAC supplies in West Newton off of 67. He aint cheap, but he has a large stock of parts.

 

[Rookie]

Mine was acting up along the same lines. There is a small rubber hose on the vacuum that was plugged. Service guy took it off, blew it out, and it worked. It might not work for you, but it doesn't cost anything.

 

[churchmouse]

If you ever get in a bind for parts there is always Shortys HVAC supplies in West Newton off of 67. He aint cheap, but he has a large stock of parts.

Shorty is a personal friend of mine. We came up through the trade together and he is/was one of the best techs I have ever known.

 

[K_W]

Ran some experiments, found that if the main blower control on the thermostat is set to "Auto" (so not running during lighting cycle) the gas is first shut off after 6 seconds then 3 seconds every time after that...

Also checked hose from inducer to vacuum switch, limit switch in heating camber (don't know proper name), visually checked caps on control board, and checked all visible wires for frays/burns.

Any new ideas based on that?

 

[K_W]

I FIXED IT

There was crud clogging the nipple on the inducer fan. The pressure switch was not getting any reading.

Thanks INGO for all the assistance.

 

[GregD]

I FIXED IT

There was crud clogging inside the nipple on the inducer fan. The pressure switch was not getting any reading.

Thanks INGO for all the assistance.

You did great, K_W

 

[K_W]

Back to 71... furnace shut itself off and all is well.

 

[churchmouse]

I FIXED IT

There was crud clogging the nipple on the inducer fan. The pressure switch was not getting any reading.

Thanks INGO for all the assistance.

That it even started the firing process is troubling to me but if it is working and you are warm.....

 

[K_W]

That it even started the firing process is troubling to me but if it is working and you are warm.....

I'm going to call Lennox in the morning and make sure that's normal behavior for the furnace. Because you are right, that is concerning.

 

[sljccj]

That it even started the firing process is troubling to me but if it is working and you are warm.....

I was thinking the same thing. It normally will not start if the flue fan system isnt functioning properly.

 

[sig-guy]

There was crud clogging the nipple on the inducer fan. The pressure switch was not getting any reading.

If the pressure switch didn't close, it would NOT have fired up in the first place.

If it was the issue, it was likely barely pulled in 'closed' and the added pressure from firing dropped it out.

BTW, flame sensing rods get dirty, they don't go bad unless a homeowner/tech breaks the porcelain.