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Old 10-18-2012, 12:39 PM   #1
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Furnace not lighting


A squirrel dropped a walnut into my roof exhaust vent for my Trane XV90 furnace. It ended up in the exhaust fan so I took it apart and cleaned it out and then put it back together. Since I reassembled it the furnace won't light. when I turn it on I do see the glow of the ignition system but I don't think the gas is turning on. also, the red light blinks 3 times which I understand indicates a vacuum failure? All the tubes, wires and hoses are connected properly and the fan housing seems to be tight and sealed etc. So water did drip down out of the exhaust system onto the gas valve switch but it's all dry now. Any ideas on what might be wrong? Also, I took two screws and two wires off of a sensor on top of the flame box I thought it was the fame sensor but it is just a flat round disk and seems to be clean.

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Old 10-18-2012, 12:44 PM   #2
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Furnace not lighting


Once after a serious rain storm on a service call for a furnace that wouldn't light up, I removed the pressure switch tube and about a quart of rain water came pouring out of the inducer fan area. Lit right up after that.

You've obviously a pressure switch not closing issue. Did you use a fire rated sealant when you re-installed the inducer fan? Is it tightly screwed in? That all has to be thoroughly tight or it will suck in external air and not be able to pull the pressure switch closed.

Did you get up on the roof and make sure there's no obstruction in your exhaust pipe? There's a good chance of that if squirrels have been messing around up there.

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Old 10-20-2012, 01:23 PM   #3
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Furnace not lighting


I think all the water drained out now, there was quite a bit built up in the fan drain tube. I'm not sure about the seals, I didn't reapply any. I assumed the existing sealant would form a adequate gasket. I will try taking it apart and reassembling it with sealant -- can I find the right stuff at home depot? Any joints or fittings other than the fan housing itself that might need sealant or tightening? Where is the fan trying to create a vacuum? Inside the ignition area (flame box?)
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Old 10-20-2012, 02:12 PM   #4
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Furnace not lighting


did the walnut damage any of those plastic fins on inducer motor.....if water got into gas valve theres a good chance its trash...ben sr
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Old 10-20-2012, 10:37 PM   #5
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Furnace not lighting


When I took the blower out again to try re-sealing it I noticed that it is supposed to have 2 different sets of fan blades/fins. One set of the plastic fan blades were completely sheared off by the walnut. It looks likes I'm going to have to replace the whole blower unit which costs about $120 online. Hopefully that solves the problem.
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Old 10-21-2012, 07:40 AM   #6
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Furnace not lighting


Quote:
Originally Posted by Mdaskew View Post
When I took the blower out again to try re-sealing it I noticed that it is supposed to have 2 different sets of fan blades/fins. One set of the plastic fan blades were completely sheared off by the walnut. It looks likes I'm going to have to replace the whole blower unit which costs about $120 online. Hopefully that solves the problem.
that is what i thougth happened ...replace inducer motor you should be good to go ...ben sr..let us know how you make out...
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Old 10-21-2012, 10:31 AM   #7
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Furnace not lighting


Read this old thread about replacing only the plastic fan wheel in the ID fan.

I no longer replace entire id fan. I keep an extra wheel on hand and rebuild about every 5-6 years.

Hope it could work for you.

Furnace will not stay on

My blower wheel: http://www.cshincorporated.com/advan...4358&x=21&y=12

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Last edited by diyorpay; 10-21-2012 at 10:42 AM.
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