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Old 02-14-2011, 10:17 AM   #1
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Bryant 394GAZ (Gas) Intermittant Heat


Hello, I have a 20 year-young Bryant 394GAZ furnace that is having intermittant heat problems. THere are some days the furnace runs and cycles fine but there are other days when the furnace never kicks on. When the furnace does not kick on I can just go down to the main power switch on the side of the furnace and turn off and on and the cycle starts up. THe typical cycle takes about 5 minutes 1) igniter lights the pilot but still clicks for about 2 minutes until 2) all the burners light, 3) burners run for a couple minutes 4) fan kicks on. (All seems normal).

I had the furnace cleaned and inspected about 2 months ago, replaced the thermostat last week (same problem with the old and new thermostat).

There does not seem to be a flame sensor rod to clean, it looks like everything is integrated into the pilot ignitor.

Any help or suggestions would be greatly appreciated.
Thanks bob

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Old 02-14-2011, 10:32 AM   #2
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Bryant 394GAZ (Gas) Intermittant Heat


Welcome Bob, to the best DIY'r site on the web.

When the furnace fails to heat, does it even try and start?

If so how far does it get in the ignition sequence?

If you could please be a bit more specific as to what trouble shooting you have already tried, this would be helpful to understand the diagnostic's that have already preformed.

Mark

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Old 02-14-2011, 11:45 AM   #3
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Bryant 394GAZ (Gas) Intermittant Heat


Sounds like it could be weak spark, weak pilot flame, or both
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Old 02-14-2011, 12:00 PM   #4
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Bryant 394GAZ (Gas) Intermittant Heat


Unfortunatly, I have not done a whole lot of any other diagnostics...

I'm sorry, the only this I know is there is no heat and it does not look like it is trying to do anything.

Sometimes I can change the temp settings on the thermostat (click it up a few degrees) or turn the fan off, to on, to auto and it will kick on but not always. Sometimes if I reset the thermostat it will kick on again but this requires me to reprogram the thermostat. This was the same with the old thermostat.

I do know everytime i use the power switch on the side of the furnace it seems to work for the entire day ans sometimes a couple days.

It does not allows happen at night sometimes it is in the middle fo the day, just no heat, the temp slows goes down under 65 and i fddle with the thermo or the power switch until it cycles.

One time I did notice that the pilot fired, the main burners fired, the fan kicked on then the main burners immediatly went off. (This was just once, which is why I looked for the flame sensor rod to clean).

Thanks for immediate response, I am sorry I do not have any more detail.

bob
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Old 02-14-2011, 12:46 PM   #5
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Bryant 394GAZ (Gas) Intermittant Heat


Quote:
Originally Posted by kenmac View Post
Sounds like it could be weak spark, weak pilot flame, or both
I am not skilled at this but I know I can see the spark and the pilot. I'm sure that your statement probably means something else.

Is this a part that could need to be replaced?
Thanks for the response!
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Old 02-14-2011, 12:53 PM   #6
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Bryant 394GAZ (Gas) Intermittant Heat


Quote:
Originally Posted by rgwekwert View Post
I am not skilled at this but I know I can see the spark and the pilot. I'm sure that your statement probably means something else.

Is this a part that could need to be replaced?
Thanks for the response!

DIY and this forum are for those who have mechanical aptitude and know something about what they are doing.

You gave it your best shot but now it's time to call a pro. .0000001% of the time does the thermostat have anything to do with furnace issues. Please stop now before you are purchasing a more costly part.
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Old 02-14-2011, 08:05 PM   #7
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Bryant 394GAZ (Gas) Intermittant Heat


Quote:
Originally Posted by seatonheating View Post
DIY and this forum are for those who have mechanical aptitude and know something about what they are doing.

You gave it your best shot but now it's time to call a pro. .0000001% of the time does the thermostat have anything to do with furnace issues. Please stop now before you are purchasing a more costly part.
Kinda harsh ... I think I have the mechanical aptitude to replace parts, if someone wants to point me in the proper direction. I thought this was a DIY site.

My apologies for wasting everyone's time...
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Old 02-14-2011, 08:33 PM   #8
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Bryant 394GAZ (Gas) Intermittant Heat


Quote:
Originally Posted by rgwekwert View Post
Kinda harsh ... I think I have the mechanical aptitude to replace parts, if someone wants to point me in the proper direction. I thought this was a DIY site.

My apologies for wasting everyone's time...
No appologies required, in fact it should be the other way around, some folks in here are just like that.

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Old 02-14-2011, 08:39 PM   #9
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Bryant 394GAZ (Gas) Intermittant Heat


I would have to assume there is some sort of flame sensor. Your best bet is attempting to clean that. If it fires then shuts off immediately I. Would lean towards that being the problem. You could also be losing gas pressure but unless you have a gas gauge that will be tough to check.
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Old 02-15-2011, 01:55 PM   #10
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Bryant 394GAZ (Gas) Intermittant Heat


Just a quick update:
I only had a few minutes to look at the furnace yesterday so I basically just cleaned contacts and connectors. Tightened a couple loose thermostat wires (yep loose RH) but still had the same problem.

Everything worked fine all day yesterday kept heat and cycled perfectly throughout the day with thermostat set for 70 but when I woke up this AM the heat never kicked on. Note: the thermostat dials down to 65 at night. I walked up to the power switch on the side of the furnace turned it off and then turned it on and it fired right up and has been working fine and keeping temp all day.

I am going to set the furnace to "hold" at 70 all night tonight and see if there is heat in the morning.

Thanks for reading...
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Old 02-15-2011, 07:23 PM   #11
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Bryant 394GAZ (Gas) Intermittant Heat


Hard to tell you from behind this computer. But, check all your wiring connections at the furnace. 24v & 110. try posting a pic of the furnace.
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Old 02-16-2011, 06:32 AM   #12
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Bryant 394GAZ (Gas) Intermittant Heat


I have a couple 25 year old Bryant gas furnaces.

Do you know what kind of pilot flame sensing device you have? Do you have any of the manuals that came with your furnace?

If you have a flame sensing rod, you can probably solve your problem by cleaning it - make it nice and shiny with a plastic scrubby. Unfortunately, it sounds like you have one of Bryant's infamous 3-wire pilot jobs which are not repairable.

If you have a pilot flame and the main burners will not fire, you can use a jumper wire to apply 24 volts directly to the gas valve. You need a wiring diagram to know where to run the jumper. If the jumper opens your gas valve and the main burners come on, it is almost 100% that your pilot flame sensing device is failing.

Last edited by artbuc; 02-16-2011 at 06:36 AM.
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Old 02-16-2011, 10:43 AM   #13
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Bryant 394GAZ (Gas) Intermittant Heat


I added a picture from my B&W stick figure camera. I will also add a picture of the pilot assembly later because I am pretty sure there is no flame sensing rod to be cleaned.

BTW - I left the thermostat set for 70 last night and the furnace performed perfectly all night, I did *NOT* have to power cycle the unit this morning.
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Old 02-22-2011, 07:15 PM   #14
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Bryant 394GAZ (Gas) Intermittant Heat


I believe we have a very similar problem on similar looking equipment. I talked to a mechanic who indicated that it sounds like I have a "lazy gas valve". As he explained, as gas valves get older, the lubrication wears out, causing the valve to be subject to sticking, or opening too slowly to allow the burners to catch, resulting in a shutdown and lockout (especially in colder temps). When you reset the system by turning off the main switch, it clears the fault and allows the system to work if the valve loosens up. Some times warming the system clears the sticking valve and allows the valve to open. I have a Carrier (looks very similar to yours), my valve is a EF32CW184A. I've tried to find a replacement online and get shunted over to a 183A as a replacement. I want to know if there is any way to check to determine if this is in fact what is happening and if this is actually the replacement valve.
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Old 02-23-2011, 09:00 PM   #15
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This sounds exactly like my problem. The furnace ran fine last week while the temps were warm for the area, then the other day we got 12 inches of snow in 12 hours and in the morning no heat, after working for 6 days. Again, all I have to do is reset the main power switch on the side of the furnace and violia - furnace is working.
I have set the furnace to hold at 70 and set the variable on the thermostat to kick on at 1 degree variance and left the door open to the furnance room, every thing seems to work for now. I know this is not a solution but until I either replace the 20 year old furnace or the gas valve, I will not be as green as I should be. I am also attaching a picture of the non-servicable 3 wire ignitor/pilot assembly.

Has anyone else heard of this "Lazy Gas Valve" problem? Are there other symptoms?
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Bryant 394GAZ (Gas) Intermittant Heat-bryant_ignitor_pilot.jpg   Bryant 394GAZ (Gas) Intermittant Heat-bryant_inside.jpg  

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