Day & Night Gas Furnace - Blower Fan Runs Continuously

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Old 01-22-11, 08:39 AM
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Day & Night Gas Furnace - Blower Fan Runs Continuously

We have a 25 year old Day & Night furnace, model #376BAW048095, that has recently gone out on us. I believe there were two issues, one being the pilot ignitor, and the other being the inducer fan. the inducer fan was making a high pitched noise prior to the failure, and pilot ignitor was having to make several attempts to light the burner. It recently gave up and now the blower fan comes on. I replaced the ignitor as one was readily available, but that did not solve the problem. Is there a way to test if the inducer fan is indeed the problem. I've check all the switches I am aware of (auxillary limit and draft safeguard), and neither seem to be tripped. If I am able to replace the inducer fan (and it indeed was the problem), are there other reset buttons that will need to be set or would furnace just operate normally?

I know the furnace should be replaced, but am not in a position to do this at this time. Thanks for any input you might have.
 
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Old 01-22-11, 06:25 PM
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I am assuming you have a continuous blower and no heat. i think I read your post correctly.
These are the things that relate to the above:

1-bad transformer
2- open limit/roll-out
3- open fuse link
4-bad board
If this is a counter-flo furnace (blower on top), check on top close to the edge for a button, usually on the right side. That is an upper limit.
 
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Old 01-22-11, 07:03 PM
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thanks for the reply.

Yes, we have continuous blower and no heat. I replaced the inducer fan & motor today (as I knew it was bad), but it did not correct the problem.

Not sure about the transformer. I unhooked the thermostat, and jumped the furnace to run continuously, but still only blower / no heat.

Could be the limit switch. I should probably try jumping around it to see. I have check the upper limit switch (auxillary limit) and it has not been tripped.

Not sure about the fuse link - is it accessed from the front or do you need to the side panel.

One of the other posts with the same problem but different brand a manual limit reset button (located behind the side panel). I don't see one on the diagrams, but I could be missing. Any ideas.

If it is a bad board, then I'm guessing it we will probably just need to replace.

Thanks again for the suggestions.
 
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Old 01-22-11, 10:02 PM
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You need to check the things MBK has suggested.

You need to check the low voltage circuit from the Transformer to the R terminal on the circuit board and determine where there is an open circuit interrupting the 24 VAC voltage.

If you can read the circuit diagram, review that circuit and series of parts, including the fuse on the circuit board, if any.
 
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Old 01-23-11, 10:10 AM
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The fuse link is found at the limit on the face of the furnace. It looks like a little silver bullet. If you have a meter, remove the spade clip with the fuse link from the limit. Now you can do continuity test across the link. If you don't have a meter, install a TEMPORARY jumper across the fuse link. And I do mean TEMPORARY, only for the test.
 
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Old 01-23-11, 11:52 AM
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Thanks to both of you for your help.

I found the fuse links (at least 2 of them - the diagrams calls for three of them, but I followed the line although back to the box and didn't come across the third). Before testing these, I tested the transformer (at the r and c posts on the board) and it showed no output, so I guess that is where the problem is. I did not see any fuses on the board. Doubt if I'll be able to find a transformer today.

thanks again.
 
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Old 01-23-11, 12:45 PM
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You can probably find a replacement 24 volt transformer at Radio Shack.



Usually transformers burn out because of a short circuit on the secondary wiring, usually on the thermostat wiring and usually because the thermostat wiring has been cut on some sheet metal, which grounds the 24 VAC circuit.

So I'd use a multimeter to check for a short to ground on the thermostat wire. And I'd disconnect the thermostat wire from the furnace, replace the transformer and make sure nothing shorts out again when you turn on the power.

Then I'd take precautions when connecting the thermostat wires again, such as putting your multimeter in series with the thermostat wire and measuring the AC amps.

That will help avoid the need to buy several transformers!
 
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