HVAC guys my furnace won't come on

[lonewolf]

Having a cold stormy night up here right now so I went and turned the furnace on for the first time this year . It is a Frigidare electronic high efficiancy gas furnace aprrox 3 years old. I turned up the thermostat and i can hear the small fan running but don't hear the gas igniting and thats all that happens.
tried a couple of times and nothing.
opened up the panels and it is pretty sealed up in there .you can't see the burners at all. I can see a few circut boards one of which has a LED on it that is lit up when thermostat is off and flashes when i turn thermostat up . Filter is allways clean.when i removed the top panel there is a small quarter size little window there . can't remember but thought maybe there was an LED in there lit up but i could be mistaken . must be for something.

I live out in the country and getting a service tech out here isn't easy but at the same time I am not sure there is much the layman can do with this sort of thing but if the experts here have any ideas on what to look for i'll try anything .

thanks
Bruce

[on-ramp]

had the same problem with mine. If you follow the line from the blower , you will see it goes into a pressure switch. When there is enough pressure in the line, that tell the switch that the blower is working and it closes the switch, goes from open to closed.
It's a small device. with 2 pneumatic lines going into it and 2 electrical contacts.

this was the problem with ours. the fan blower would come on, but the furnace wouldn't ignite the burners because the defective switch would not close the circuit.
The switch is about a 30 dollar part. you may have to remove it to get the part no. from it. Make sure the furnace electricals are all shut down before removing the switch.

To prove this was the culprit, i had to bypass the switch all together (temporarily) but manually closing the contacts, make an electrical jumper, and the burners ignited

[stealthn]

I will assume the power switch and gas are on. Look in that little window for the LED to be lit. When you turn it on with the top cover removed do you see the glow plug light? It could be the fan motor seized, glow plug, or just loose wiring in the lower circuit board (just re-tighten the screws all the wires go into)

Happy heating

[on-ramp]

Another thing, when you put the door back on the furnace, there is another safety switch that senses the door is on. that's the only way the burners will come on. make sure this switch is fully pressed when the door is on.

[einreb]

the ignitors go bad on a regular basis. i swear they engineer these things to fail.

http://www.google.com/search?q=gas+furnace+ignitor

[on-ramp]

ignitors will not fail only after 3 years.
most likely a sticky pressure switch

[dad911]

Originally Posted by on-ramp

ignitors will not fail only after 3 years.
most likely a sticky pressure switch

I disagree. In the past 10 years, the only failures on my high efficiency furnaces have been the ignitors. I now keep spares ready by the furnace.

[einreb]

Originally Posted by on-ramp

ignitors will not fail only after 3 years.

Yes they will.

Originally Posted by on-ramp

most likely a sticky pressure switch

I dont agree.

[lm6y]

Do a continuity check on the ignitors, or a voltage test if it's easier. My original ignitor lasted three years, and one every other year after that. I too keep a spare one just in case.

What kind of unit is it?

The blinking LED makes me think a failsafe has tripped. Whether it's the pressure sensor for the exhaust blower, the safety switch on the door, a bad ignitor, or even a bad circuit board.

In the manual, it should have a sequence of operations chart ( this happens, then THIS happens, and then finally this happens). You just have find out which step makes it fail.

I know from diagnosing mine, that if the door switch is off, nothing happens. Not even the exhaust blower runs.

Good luck with it!

[lonewolf]

Wow thanks for the responce guys.
this is a frigidare furnace ,don't have the manual, came new with house.
the small fan comes on when i turn up the thermostat but ussually after 5 seconds or so i hear the gas click on and igniting then the large squirell cage comes on .
Now only the small fans runs but thats it .
the one led is on the circut board on the left . it stays on but flashes when i turned on thermostat. the furnace ran a month ago and has never had any issues.
here is a pic .
on my old furnace i could see inside and see the ignitor light up but as you can see here it is pretty sealed up.

[dad911]

Either visually inspect the ignitor, or check it's continuity. They burn open like a fuse when they fail.

[turbo6bar]

Get the model number. Go to the manufacturer's web site and download and user's manual. The manual will outline the furnace startup process. It will also decode the flashing LED light, which generally tells you where the failure lies.

I do not deal with the higher efficiency units, but on lower end units, the gas valve will still open if the igniter does not burn hot. When ignition does not occur, the gas valve closes and the system cycles once or twice again before kicking an error code. Your unit may act differently.

You really do need a professional or a manual to safely troubleshoot.

You can test the pressure switch connected to the induced draft blower (small fan) by checking continuity. When the system is off, the switch should be open. When the induced draft blower turns on, the switch should close.

[lonewolf]

Hi guys
this morning the furnace came on like normal .
still on now . this unit has an electrical condensation remover on the side of the furnace . takes condensation out of the air and the moisture ends up in the little tank and then is pumped out of the house .
i noticed the line was full of water and removed last night from the tank and let it gravity drain over night . not sure if that was the cause or not .
i see now when running there is a yellow LED lit up on the circut board as well as the red one .
the small glass window you can now see the gas burning through there.
i am going to let it run for a while and dry up all the moisture if any in the system.
hopefully all is well.

thanks to everyone who responded . i really appreciate it .
i will download a manual. laying in bed this morning i figured i better do that before doing any kind of testing on this type of electrical setup.
thanks again guys
Bruce

[Nostril Cheese]

Originally Posted by on-ramp

ignitors will not fail only after 3 years.
most likely a sticky pressure switch

They most certainly will fail. I've replaced one that was 6 months old.

That would be what I would check first.