I need help with my furnace

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swanee

New member
I returned from vacation last night and set the thermostat temp back up to 70 degrees. The house has not gone past 65, right now it is 64. The furnace will kick on for a few minutes with heat coming through the vents, however it will shut off after a few minutes and then half hour later it will kick on again. Its a gas furnace and the house/furnace is 10 years old.

Does anyone know what this could possibly be and if I need to have a HVAC guy come out? Thanks for your help.
 
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skeeter2010

Member
I would check a couple things is the exhaust pipe blocked outside with or snow is the condinsate drain working /draining
Just the simple stuff
 
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snowshoe

Member
Find the PVC pipe that is your vent and make sure nothing is blocking it not just outside but inside. I had a dead chipmunk in mine and had the same problem.
 
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98panther

New member
Yeah that's the first thing I'd check, in the very cold, Ice will build up at the vent and do exactly that.
Every year I have to do a late night run to my mothers to check her furnace.

It tries to run correctly but gets choked at the exhaust, and shuts down.
 
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swanee

New member
Thanks guys. I was just outside and looked and there was nothing visible blocking it. The furnace is running right now and I noticed that there was plenty of exhaust coming from the vent. I am going to look up there with a small mirror (trying to locate at this time) as with the 45 degree elbow you can't see much.
 
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uperjim

Member
It may have corrected itself---could have been ice buildup in the exhaust due to condensation.

I just got back from my cabin and while at the cabin I heated with wood for almost 2 weeks. When we left i kicked the propane furnace back on and the burner backfired was yellow in color sort of a floating flame indicating that the exhaust (vertical b-pipe) was partially plugged and actually turned on the smoke detector but the furnace ran. I let the furnace run for awhile and then turned it off, waited 10 minutes and started all over again---this time no problems. I think the b-vent was partially plugged with ice due to the weeks of condensation without any real heat in the pipe to melt it off---at least that is my guess.
 
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mschu2008doo

New member
I have this problem all the time. In the furnace by where the burners are there is a sensor. It has a wire going to it from the gas valve. It is in the front of the the burners where the gas comes out, usually on the left, it looks like a little medal rod. You need to take a piece of fine sand paper or a green brillo pad and clean it off. This sensor gets build up on it and short cycles the furnace. It will look like nothing is on there but there is. Just remember to shut off the power switch on the side.
 
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wags

New member
Possible limit switch issue.

Gas fired units as mentioned work like this: T-stat calls for heat, gas valve opens, either standing pilot or elect spark fires burners then a device called a limit switch senses when the temp in the chamber goes up to a preset temp and starts the fan to blow the heat through the system, once the t-stat get satisified the reverse happens, the limit switch senses the drop in temp once the gass is off and shuts down the blower.

Does the fan go on and off, (cycle?) How much time between the cycle? does the gas shut down when the fan goes off or does it stay on until the fan starts again?

Just a few things to help figure this out.

Dan
 
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snow_monkey

New member
The furnace is shutting down for a reason. When the burners get dirty the flames will be uneven causing the sensor(spill switch) to cut out. The spill switches are similar to a fusable link. The spill sensor should be located on a access door to the furnace burners. Worst case senario a cracked heat exchanger. If you see evidence of soot or burn marks on the inside of the door you may have to clean the burners and get a new sensor. When in doubt call an expert.
 
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chadlyt

Member
do you have a programmable thermostat? mine went on the fritz and it would run the fan for 2 minutes at a time.

I replaced it, and it was fine.

This was after having a repair tech come out and say everything was fine on the furnace side.

Maybe something to think about.
 
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swanee

New member
I'll try to answer what I can here. And thanks so much for your help. I timed a heat cycle earlier and it was 23 minutes that the furnace was running.

There is water running out of the pipe so that is not clogged up.

A couple times earlier today it seems that when I tripped the breaker (on/off) it would start the furnace back up.

I opened the two panels and did not notice any soot buildup on the panel. There is an LED light that is supposed to blink to show what is wrong. It is not blinking, when I hold the switch in for the panel to keep the LED light on it comes on and then shuts off. The manual says that "its not getting power", however I know that the unit is getting power.

The temp got up to 65 in the house earlier, keep throwing suggestions at me. I will clean the sensor shortly.
 
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jeepbob47

New member
Furnance

The sensor is actually an electronic ignitor. I have had the same problem. Look and see if the ceramic housing is cracked. If it is you need to get a new one. If the metal part of the ignitor is tarnished then make it shiney with sandpaper and re-install. Hope this helps.
 
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racerx_96

New member
I've had similar situations. In one case it was a differential pressure switch (I think). There are two small hoses running to a round (as you are looking at it, about 3-1/2" diameter) sensor. I was able to get the furnace to run until the service person arrived by blowing/sucking on the small hoses. The furnace would cycle (run until up to temp.), then when I would feel cold, I would repeat the process. It wasn't the best situation but the temps were -10F on a Sunday evening. The other time it was the actual exhaust blower for the flue gases. In my case that is housed in a black plastic housing with your pvc exhaust pipe running from it and another 2-1/2" pvc pipe running to it. That should start to run as soon as your burners are lit. There should be a small viewing/access hole in the front (again, as you are looking at it) that you should be able to verify that it is spinning. In my case, the bearings siezed up TIGHT.
1st situation was $100 bill for service (including part).
2nd situation was $200 bill for service (part under warranty (I hope, still waiting), otherwise another $200 for the part).

Good Luck
 
chords

chords

Active member
The sensor is actually an electronic ignitor. Look and see if the ceramic housing is cracked.

Look real close. Use a magnifier glass to find a hairline crack on the ignitor.
 
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freezinbevr

New member
What doomsman said. Check the filter. If you use the $2 cheap fiberglass filters, it will eventually plug the AC coil above. Is there good airflow out of the registers?

Could be a bunch of things. The remote flame sensor is a very common issue. Don't clean w/a very rough sand cloth though, it will score the rod and collect that much more oxide on it after. If the sensor cleaning does the trick, still get a replacement to exchange. It WILL happen again shortly.
 
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