Sorry, I'm not sure if this is the right forum, but …

My furnace won't light. It starts the exhaust fan, the igniter gets red hot, the gas valve actuates (you can hear it click, hear flow and smell a bit of gas) for a few seconds, then after it doesn't light then it shuts the valve, the exhaust fan runs for a minute or so, and then it repeats 2 more times before shutting down and turning the air handler on. At that point it gives a 2-blink error. This is a Trane XB80.

Any ideas of something easy? Trying to avoid a huge expense before the end of the year if it's something I can figure out. And if it's just time to call someone, any recommendations for a quality HVAC service in Houston? We are in Shady Acres (near oak forest).

JP76 said:

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Clean your flame sensor

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Wouldn't that only be an issue if it did light and then shut off?

It blows but doesn't light the gas to add heat, correct? If so, the motherboard may be the issue. Had the same thing happen a couple years ago and had to get the motherboard replaced. My step brother did it at cost, which was about $300.

If your igniter is red and you hear the gas valve click and smell gas it should immediately light. If the flame sensor doesn't sense the flame within 3-5 seconds it will shut off and try again three times.

I'd venture to say you don't have sufficient gas pressure or a bad gas valve if it's not actually firing. If it's firing for the 3-5 seconds and not staying on it's likely a flame sensor.

One last thing is it could just be air in the lines. Unplug the furnace once it faults out and try again. After two or three unplugs you should have the air out.

Let us know what you end up finding.

It's been a year or two so I don't remember the exact way the furnace was acting but I had a pressure switch go out on my furnace. Easy to swap out on my own and haven't had trouble with it since then.

https://dengarden.com/appliances/Everything-You-Need-to-Know-About-A-Furnace-Pressure-Switch

JP76 said:

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Clean your flame sensor

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Do this before doing anything else. This is free, takes 45 seconds and is likely the culprit.

Wild Ass Guess... Take the hose between your exhaust fan and controller off and blow/clean it out.

I've seen it do some weird things even when it wasn't completely clogged.

You asked for easy..

I had something very similar just happen. The manifold near the igniter has rusted, and rust/debris had clogged a gas orifice. It took some effort, but we removed the entire gas manifold/tube system, cleaned it off, blew it out, reinstalled it, and it works great now.

Milwaukees Best Light said:

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JP76 said:

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Clean your flame sensor

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Do this before doing anything else. This is free, takes 45 seconds and is likely the culprit.

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agreed. also try this trick for the pressure switch. This got mine running 2 years ago until I replaced it.

rilloaggie said:

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It's been a year or two so I don't remember the exact way the furnace was acting but I had a pressure switch go out on my furnace. Easy to swap out on my own and haven't had trouble with it since then.

https://dengarden.com/appliances/Everything-You-Need-to-Know-About-A-Furnace-Pressure-Switch

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For me, mice had chewed through the tube going from the exhaust to the pressure switch. $0.50 at autozone.

OP, your control board may have a digital readout with a code telling you what the problem is. Remove the panel and press the button to energize the board for troubleshooting.

DX2011 said:

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Sorry, I'm not sure if this is the right forum, but …

My furnace won't light. It starts the exhaust fan, the igniter gets red hot, the gas valve actuates (you can hear it click, hear flow and smell a bit of gas) for a few seconds, then after it doesn't light then it shuts the valve, the exhaust fan runs for a minute or so, and then it repeats 2 more times before shutting down and turning the air handler on. At that point it gives a 2-blink error. This is a Trane XB80.

Any ideas of something easy? Trying to avoid a huge expense before the end of the year if it's something I can figure out. And if it's just time to call someone, any recommendations for a quality HVAC service in Houston? We are in Shady Acres (near oak forest).

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Flashing 1 and 1 ?

Or 2 blinks and 2 blinks ?

I think 1 and 1 just means it is going into lock out mode from failing to stay ignited

My bet is still on the flame sensor

I think OP must have frozen to death last night. Sad really.

Milwaukees Best Light said:

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I think OP must have frozen to death last night. Sad really.

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LOL, sorry for the lack of update!

It was the rail, well the orifice on the rail that blew over the igniter, was mostly blocked causing a lack of pressure. Easily cleaned and cleaned the others in case while I had it loose.

15 minute fix, and I wanted to avoid having a HVAC company tell me that it couldn't be fixed and we should replace because the furnace is almost 20 years old, if it didn't need to be.

We had some very unscrupulous HVAC techs when diagnosing our AC a few years ago. It did need to be replaced, which wasn't a surprise, but the use of meters (touching metal to get it to go off repeatedly) and other jokers was funny to watch. That paired with the multiple companies that refused to replace the AC without the furnace got on my nerves quick.

Josepi said:

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I had something very similar just happen. The manifold near the igniter has rusted, and rust/debris had clogged a gas orifice. It took some effort, but we removed the entire gas manifold/tube system, cleaned it off, blew it out, reinstalled it, and it works great now.

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Winner

What do I win!!!