# Furnace Advice Needed



## gunit (Dec 29, 2008)

Hello to all,
Just wanted to see if I can get some helpful advice from someone who knows about furnaces before I called someone in to fix it, maybe my problem isn't too bad and I can fix it myself!

My furnace seems to be having some problems, here is a brief description of what his happening.

The furnace appears to be working and heating but after about 3-5hrs, it will just quit. So at first, I would turn up the thermastat as high as it goes to see if the furnace would kick in, it wouldn't, but then when i turn it "on" to the fan, it works. Then i went to the furnace itself and opened up the unit (after turning off the power) and made sure all the wires, etc were good, it appears there were no loose wires and the one fuse appeared to be in good shape, I also changed the furnace filter at the same time. for me to get the furnace working again, I have to flip off and on the breaker switch, the furnace will kick in and I hear it "flaming up" and then the fan goes on.

So basically, I do that before going to sleep and before i leave in the mornings, but the furnace is staying on for less and less time now.

Any advice would be greatly appreciated.


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## glennjanie (Dec 29, 2008)

Welcome Gunit:
First check the limit switches and relays for proper function. Check the vent flue from the burner to the roof and rid any bird nests or spider colonies.
If the furnace has a board in it, you could check the board for burned spots, chared resistors and transistors.
One member recently went through a long list of troubleshooting and finally discovered the door switch was not engaging properly.
Glenn


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## d.scott (Jan 1, 2009)

if this is a gas furnace,which i am assuming,your problem, is in limit switch.when you diconnect power,reset,this resets limit switch.problem could be many things.time to call a tech.  d.scott


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## Icehouse (Jan 10, 2009)

See below 

 1. Thermostat calls for heat.

2. Draft inducer motor starts.

3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure  produced by the draft inducer and closes.

4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small metal probe about 1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas.
Solution: You probably need to purchase and install a new ignitor. I would suggest that you inspect your ignitor closely for cracks. Make sure you do not touch the ignitor with your bare hands. If you do not visually see a crack, then you could have a furnace control board problem or a limit, rollout switch problem.  
The furnace's control board might not be supplying the voltage to the ignitor. If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you need to clean your flame sensor with light sand paper or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.


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