Ultra SX90 main burners

[Jeff Gramza]

Furnace is around 20 years old. Sometimes the main burners light and sometimes they don't. When they don't, I go downstairs, turn the blower motor off and flip the black switch to 'off' on the little beige box (smart valve?). Wait 30 seconds, reverse the process and the main burners come on. They may come on the next few times but when it starts to get cold in the house, I go downstairs and see the main burners haven't fired up. Doesn't appear the plastic hoses are clogged. Any suggestions where to start looking?

[trader_4]

Are you sure they are not lighting or are they lighting, then going out? If it;s the latter, could be a bad flame sensor. If it won't light at all, what is the lighting method? Pilot light? Hot surface igniter? Is it high efficiency with a blower for combustion? Could be a pressure switch, blocked vent to the outside.

[hubops]

Elon Musk's rockets are having the same ignite problems !

John T.

[Dean Hoffman]

It seems odd that the blower motor is actually running. (figure of speech?) The motors on the few furnaces I've had were started by some sort of heat sensor. So maybe the burners light, the motor starts, and.............................?

[Clare Snyder]

My blower motor runs constantly (at low speed) and just ramps up to higher speed when the furnace lights and the plenum temperature comes up.

[Clare Snyder]

I suspect your problem is the same as on the neighbor's Tempstar - the hose from the inducer motor gets condensation in it and eventually the port itfice in the blower housing restricts to the point the vacuum/pressure switches don't get the proper signal any more. Try blowing through the hoses that connect to the inducer blower- if you can't blow into the blower you will need to ream out the fitting - sometimes a paper clip will do it - sometimes you need a drill.

[micky]

He did so well until the end. I woudln't pay to ride on one of those. You'd have to pay me.

[Tekkie©]

On Wed, 03 Feb 2021 14:17:04 -0500, Clare Snyder posted for all of us to digest...

burners haven't fired up. Doesn't appear the plastic hoses are clogged. Any suggestions where to start looking?

Bingo! Small drill bit, not surgery, just to clear the orifice.

[Tekkie©]

On Thu, 4 Feb 2021 11:28:46 -0800, Bob F posted for all of us to digest...

Good one!

[micky]

Good question. Unless I get very sick or want to buy a chateau in Europe, I have enough money to live on for the rest of my life. In fact I can't stop economizing even though I want to. I probably need a new laptop and I seem to have a $400 limit, for no particular reason. I'm sure everyone else here spent more than that. (and knowing me, I'll probably fix the old one or spend less than 400.) So why would I risk my life for money? For the view? For the excitement? Those would be nice if there were not such a high chance of dying. (yes, I know, the death rate hasn't been that high, but I think the last 50 years have been beginner's luck.)