# Furnace



## cruisin california (Jun 17, 2011)

Hi there! New member with a question regarding my furnace. My a/c unit works great, but when i turn on the furnace, nothing works. I took the unit out, and tested it and the blower worked. I reinstalled the furnace and still nothing. I did notice that the a/c unit has a red flashing light. Is that a sign? It seems to me that the furnace is not receiving the signal to turn on. Should i replace the board in the a/c unit? Any advice would be greatly appreciated. thanks.


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## H2oSprayer (Aug 5, 2006)

Hey look at that....another 2004 28BHS!! The red flashing light in the AC unit indicates that there is 12 volts to the circuit board; it is normal operation to see a constant flash. If it begins to flash in a pattern, that is when there is a need for concern. Have you checked the furnace fuses in the power distribution center?


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## duggy (Mar 17, 2010)

Other than using the same thermostat, the AC and furnace are two unrelated units.
This might be a silly question, but did you have the propane turned on. Light a burner on the stove, to purge the lines.


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## cruisin california (Jun 17, 2011)

duggy said:


> Other than using the same thermostat, the AC and furnace are two unrelated units.
> This might be a silly question, but did you have the propane turned on. Light a burner on the stove, to purge the lines.


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## cruisin california (Jun 17, 2011)

yes, the propane is full and purged. When i turn on the heat using the remote, i hear a click down in the furnace unit, which tells me the a/c is relaying the info. to the furnace. I have removed the batteries to the remote and reset it, also. I thought maybe the computer board up in the a/c was not relaying down to the furnace. When i pulled the unit out and put it to a jumper, the blower worked without problems.


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## Insomniak (Jul 7, 2006)

There are several clicks and clunks that could help identify the problem. Do you hear the igniter clicking? If you do, you may also hear a louder "clunk" when the gas valve opens. It's easier to hear these sounds outside with your ear close to the intake and exhaust openings for the furnace. Common problems are the sail switch which determines if there is enough air flow to ignite, the igniter could be bent or broken, and the gas valve could be bad (had that happen last year). Less common would be control board failures.


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## cruisin california (Jun 17, 2011)

Insomniak said:


> There are several clicks and clunks that could help identify the problem. Do you hear the igniter clicking? If you do, you may also hear a louder "clunk" when the gas valve opens. It's easier to hear these sounds outside with your ear close to the intake and exhaust openings for the furnace. Common problems are the sail switch which determines if there is enough air flow to ignite, the igniter could be bent or broken, and the gas valve could be bad (had that happen last year). Less common would be control board failures.


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## cruisin california (Jun 17, 2011)

Thanks for all the responses. I'm not familiar with the sail switch. Can you elaborate on that more? It seems like something electrical, because i pulled the unit out and tested it and furnace worked fine. I'ts when i reinstalled the unit that it no longer worked. As far as the clicking noise, it sounds to me like when using the remote to turn on the furnace, i hear a small click (like it is receiving signal) and that is it. Thanks again for all of your help!


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## cruisin california (Jun 17, 2011)

cruisin california said:


> There are several clicks and clunks that could help identify the problem. Do you hear the igniter clicking? If you do, you may also hear a louder "clunk" when the gas valve opens. It's easier to hear these sounds outside with your ear close to the intake and exhaust openings for the furnace. Common problems are the sail switch which determines if there is enough air flow to ignite, the igniter could be bent or broken, and the gas valve could be bad (had that happen last year). Less common would be control board failures.


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## cruisin california (Jun 17, 2011)

How do you determine if your gas valve is bad, and where is the valve located your speaking of? Thanks again


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## Insomniak (Jul 7, 2006)

The sail switch is like a little flag on the end of a stick - it sits in the combustion chamber and when the fan comes on, it will move with the wind generated. If there's enough air moving, it will close it's switch and send a signal for the igniter to start sparking. When the igniter comes on, you'll hear a rapid tick-tick-tick. If all is good, the gas valve (which is located inside the furnace where the propane line comes in) will open and you'll hear a single "clunk", then a big "whoosh" as the propane ignites. If none of these occur, the furnace fan will run for a minute or two to purge any propane in the combustion chamber, then turn off. It will repeat that sequence a couple of times before giving up. Did the furnace actually work on the bench & was it connected to propane?


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## cruisin california (Jun 17, 2011)

It was not hooked up to propane when i had the unit out. But all the other clicks and clunks were working and the blower turned on when i had it on the bench.


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## Insomniak (Jul 7, 2006)

cruisin california said:


> It was not hooked up to propane when i had the unit out. But all the other clicks and clunks were working and the blower turned on when i had it on the bench.


I would try it again on the workbench with propane attached. If it doesn't light, take a look through the sight glass and see if the igniter is sparking. It's not always easy to see, so a darkened garage will help. If you're getting a spark and the gas valve is definitely opening, take a look at the propane tubing and the orifice for blockages. Sometimes insects will get in there and spin webs, clogging everything up.


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## Bob in Virginia (Jul 15, 2010)

Whenever I will be running my furnace, I run the stove for a couple of minutes to purge the air out of the system and to make sure good propane is right there by the furnace.


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## cruisin california (Jun 17, 2011)

Thanks. i'll try that on Monday and see what happens. i'll repost with results, thanks again!


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