HVAC Help? Furnace acting up

[CraigSca]

This may be the wrong forum, but I thought I'd give this a shot anyway.

I have a 5 year old gas furnace, and, of course, on the coldest day of the year (about 15 degrees now with winds in the 20s) it has decided to conk out. Temperature in the house got in the low 60's, so I ran downstairs and checked the furnace. Not surprising, it's not on, so I head to the circuit breaker and check to see if it's tripped - it's not. I turn it off and back on and immediately the furnace starts firing up - mission accomplished, right? Nope - after about 20 minutes the burners shut off and cold air gets pumped throughout the house.

Here's the sequence I'm seeing: Temperature drops below the thermostat's setting and the inducer fan kicks in, the electric ignitor lights up and the burners catch fire and then the blower kicks in - all is well. Eventually, after about 15-20 minutes the burners turn off without any kind of signal or warning. The blower's still on and remains so for an indeterminate period of time. Eventually, the thermostat kicks in again causing the ignitor to attempt a re-light. However, either the burners never turn on or they light for a couple seconds and turn off again. Rinse, lather, repeat. If I let it stay this way, I can eventually reset the circuit breaker and we can repeat the 15-20 mins of heat cycle. Otherwise, I've never noticed the heat (burners) turning back on.

Here's what I'm attempted thus far:

Replaced the air filter.
Checked the condensate to make sure it was draining properly. It seems to be.
Ignitor seems to be working properly.
Thermostat seems to be working fine.
Checked inside, no dust build-up or obvious wiring issues.

I'm at a loss as to what it could be. I'm thinking there's possibly some kind of internal temperature sensor (perhaps the fan/limit switch) that's shutting off the gas. However, nothing has changed (to my knowledge) that would cause the internal temperature to rise and make the switch kick in - I've done no fiddling with the furnace (besides normal air filter changing) in the past 5 years.

If anyone has anything for me to try, I'd love to save myself the huge amount of $$$ it's going to take a technician to diagnose the problem.

[wheels]

Craig,

Make sure your outdoor vents are unobstructed. Ours get covered in snow sometimes and prevent the furnace from working.

[CraigSca]

Thanks for your input - I checked them last night and it was obstruction free (we've had no snow here this year).

Oddly enough, I think it's still the culprit. The winds were gusting to 40 mph yesterday and died down about 2:30am last night. I fired up the furnace again and lo and behold, the furnace stayed on all night and is running right now. I'm thinking that the high winds are somehow coming in the outside flue vent and choking out the furnace. My next question is "how do I prevent this from happening in the future?" The outside "vent" is a 4-inch PVC pipe that points down to the ground.

[Mr. Wednesday]

If you had 40 mph winds blowing across the mouth of the air intake, I could see there being issues with it pulling a vacuum on the intake. The way to address that would be to do something to shield the intake.

Edit: Alternatively, a more powerful intake fan might work as well.

[Mr. Wednesday]

Dola, and I would think that anybody selling furnace systems would have intake designs that wouldn't have problems with wind. I haven't had any problems with my furnace when it's windy, but I don't know how high the winds have gotten while I've been living in my house.

[MizzouRah]

http://www.selfhelpforums.com/archive/index.php/t-684.html

This is all I could find.

[CraigSca]

I think we can put this to bed. Low winds today and the furnace stayed on all day.

If no one else adds anything, I'm guessing this thread is done. But you never know, someone could say something crazy or add an inflammatory math problem and next thing you know Maximum Football thread, look out!

[MizzouRah]

Pass gas by it and see what happens!