Day & Night Gas Furnace Won't come on


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Old 12-06-09, 02:53 PM
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Day & Night Gas Furnace Won't come on

Does anyone know what trouble code this is? light comes on for about 5 seconds then, it blinks three times(short). I don't have the owners manual. This is a Day & Night Model number 373LAV048075. I get 27.7 volts on the transformer. The inducer motor does not come on (no power to it)no power to the hot surface igniter or the high limit switches. Blower comes on when set to fan on.

Any suggestions, will be appreciated.
 
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Old 12-06-09, 03:24 PM
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Have you tried to shut off the furnace switch itself, for say 30 seconds, and turn it back on to see if it resets itself, and comes on?

It may have tripped out on it's last sequence on a high limiit or roll out switch. Check every little device you can see on that furnace and make sure there are no devices with 2 wires that have a little reset pin inbetween the wire terminals. If you find anything like that, push it in and pay attention to if it clicks.

Do you have a 3-wire pressure switch? If so, and that is stuck open upon start up, it will not start the inducer, nor anything else after that. That can be ohms tested to see if that is the case, with a volt-ohm meter. Or you can jumper the wires hooked from NC to C, just for a test only.

Where is the thermostat?: On a wall or on the furnace? You could also also have an issue where power not going to or from the stat. Would you know enough how to test for that?

There is a relay involved also, with inducers. (I have had to replace bad ones.) You have to have 24 volts through the thermostat first, and then the relay converts it to 120 volts, to get to the inducer.

I do not know what that particular code is. But sometimes codes can be misleading anyway. I mentioned a few of the gas furnace generic basics needed to get the inducer going.

And if you actually tested the inducer does not have power in the wires leading to it(did you test that?), then we can rule a seized up inducer.

Make sure all electrical connections are good. Even remove connections and reinsert if need be, so then you will know.
 
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Old 12-06-09, 03:28 PM
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There is usually a "cheat sheet" pasted on the inside of one of the service panels that describe what each blink code means.

Just off the top of my head I would suggest that you are either not getting a run signal from the thermostat or else the draft proving pressure switch (or its wiring) is defective and showing a draft before the combustion air blower is powered. It could also be a false flame signal, i.e. flame detected before there should be a flame.
 
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Old 12-06-09, 04:18 PM
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Only with a 3-wire pressure switch could the switch be stuck open. Not with a 2-wire, since the motor has to run first.

It be nice to know if this furnace has ran already this heating season, or if this is the first time. IF the first time, it may have corrosion or stickiness.
 
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Old 12-06-09, 04:24 PM
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Sorry, forgot to mention this is an attic horizontally mounted FAU; the Thermostat is on the wall in the living room, Not sure how to test for power on it, this is a digital Tstat; I turned it to heat and auto with the panels off on the furnace, as soon as I push the door switch, that's when I see the trouble code light. I have unplugged and reconnected the power cord to the unit to see if that reset the unit; it did not. It has a two wire pressure switch, I checked to make sure the hose was in good shape, I blew into it towards the inducer motor, it is clear, I sucked on it I felt the switch close.

First time trying to use this season. Last time used last year.
 
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Old 12-06-09, 04:31 PM
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Jumper the white and red thermostat leads at the furnace and then hold in the blower door safety switch. If this causes the furnace to operate then the problem is with the thermostat or wiring.
 
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Old 12-06-09, 04:41 PM
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Originally Posted by Jrs_58 View Post
It has a two wire pressure switch, I checked to make sure the hose was in good shape, I blew into it towards the inducer motor, it is clear, I sucked on it I felt the switch close.
Do what furd says first so that everyone here can move on - if necessary.

Also, look and see if you can find a small 3 amp fuse on your control board, if jumpering does nothing.

It is not the pressure switch because with a 2 wire, the 120 volts has to make the motor run first, to then spin the fan, which then closes the pressure switch 24 volt contacts, to send power on it's way to the ignition process.
 
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Old 12-06-09, 05:10 PM
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I guess I'm not as young as as I used to be. With the thermostat in the off position, I went in the attic and jumpered the Red and white and red contacts then pushed the door safety switch. No change; I then jumpered the red and green, this turned on the blower motor only. I also found the 3 amp fuse on the circuit board ; it's ok
 
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Old 12-06-09, 05:13 PM
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Well, at least you know that the low voltage transformer is okay and that there is something wrong at the furnace rather than at the thermostat. Not having the schematic of your furnace and not being at all familiar with the brand I have nothing more to offer, sorry.
 
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Old 12-06-09, 05:27 PM
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Thanks for your help I appreciate your input. I do have a photo of the schematic and photos of the controls. Unfortunately I don't know how to attach them to the message. this is my first time at this site may be later on i'll figure it out. again, thank you.
 
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Old 12-06-09, 07:47 PM
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To post pictures you need to first upload the pictures to a photo hosting site such as photobucket.com or villagephotos.com. and then post the public URLs for the pictures (or album) here. More pictures are always better than fewer. Please have CLEAR pictures and have both close up pictures and ones from a far enough distance that we can see how the various parts are interconnected.
 
 

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