Bryant furnace clicking


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Old 02-07-10, 12:20 PM
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Bryant furnace clicking

Hello,
I have a 1988 Bryant 399A Plus 90 furnace that I am having problems with. The 3-wire pilot safety switch does not seem to be staying hot enough to keep the switch closed as it is rapidly clicking open and shut. I confirmed this by testing the voltage at the NO output of the flame sensor and it was rapidly switching between 24v and 0v.

This seemed to be identical to the symptoms posted here- http://forum.doityourself.com/gas-oi...g-problem.html so I replaced the pilot safety switch.

Well, this worked for about one day and then the problem returned. The pilot flame seems to be ok but it does flicker somewhat. Any advice on what might be wrong?

Thanks,
Sean
 
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Old 02-07-10, 12:41 PM
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An inadequate gas supply could be a cause of this problem.

Do you have natural gas or propane? Do you associate this problem with unusually cold or wet weather conditions?

Do you have other gas appliances? If so, are their any suggestions that they may have smaller main burner flames than usual?
 
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Old 02-07-10, 01:20 PM
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The flickering could be caused by a cracked heat exchanger. Take a Carbon monoxide reading at your flue pipe outside if you get a reading over 200ppm you need a new furnace.

If you don't have a carbon monoxide reader, remove the flue pipe from the inducer motor and smell if it stinks like unburnt propane, if it does your secondary heat exchanger is finished and you'll need a new furnace, I wouldn't be surprised if this is your problem on a 1988 furnace, Theres not alot of Bryant's out there 21-22yrs old that havn't had the secondary heat exchanger fail.
 
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Old 02-07-10, 01:35 PM
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It uses natural gas and I did notice the problem gradually started whenever it was raining. It is not raining today yet and it has been unseasonably warm here (I live in Seattle as well).

I have a gas cooktop and fireplace but haven't noticed any significant decrease in flame.
 
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Old 02-07-10, 01:43 PM
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I'm aware that you are using natural gas, but the smell you get with incomplete combustion is that off unburnt propane (Don't know why it just is) if you want you can pull out the blower from the bottom compartment and look up at the secondary with a flash light, I'm willing to bet that it is all white and brown full of corrosion.
 
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Old 02-07-10, 02:19 PM
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Originally Posted by shroomy
I'm aware that you are using natural gas, but the smell you get with incomplete combustion is that off unburnt propane (Don't know why it just is) if you want you can pull out the blower from the bottom compartment and look up at the secondary with a flash light, I'm willing to bet that it is all white and brown full of corrosion.
Sorry, was replying to SeattlePioneers's question.

I don't have Co2 tester so I will pull off flue pipe and have a sniff.

Regarding the pilot flame, should it be pretty still? There is definitely some draft causing it to flicker.
 
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Old 02-07-10, 11:08 PM
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Originally Posted by shroomy
The flickering could be caused by a cracked heat exchanger. Take a Carbon monoxide reading at your flue pipe outside if you get a reading over 200ppm you need a new furnace.

If you don't have a carbon monoxide reader, remove the flue pipe from the inducer motor and smell if it stinks like unburnt propane, if it does your secondary heat exchanger is finished and you'll need a new furnace, I wouldn't be surprised if this is your problem on a 1988 furnace, Theres not alot of Bryant's out there 21-22yrs old that havn't had the secondary heat exchanger fail.
Ok, got the furnace to run for about 10 min despite rapid clicking. Turned off furnace, pulled flue vent and sniffed around but didn't notice any disernable odor.

After staring into the burner box, I realized that I am not able to fully determine if pilot is moving because it is under the burners and there is only tiny hole to look thru. It does appear to be a strong blue flame though.

What I did notice that I hadn't before is that after pilot lights, the spark electrode continues to spark every two seconds or so, and keeps sparking until flame sensor clicks.
 
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Old 02-08-10, 02:59 AM
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Cleaning the pilot orifice can solve a variety of problems with these furnaces. Do that and see what happens.
 
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Old 02-08-10, 07:54 PM
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I cleaned out the orifice with compressed air and it seems to of helped. It is still clicking but is now stopping after the blower motor starts up.


Originally Posted by SeattlePioneer
An inadequate gas supply could be a cause of this problem.

Do you have natural gas or propane? Do you associate this problem with unusually cold or wet weather conditions?

Do you have other gas appliances? If so, are their any suggestions that they may have smaller main burner flames than usual?
I'm wondering if this could be the problem since it is worse when it rains. How does the rain affect the gas supply?
 
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Old 02-08-10, 09:04 PM
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Gas mains and regulators can get filled with water during heavy periods of rain. That's a low probability event, but possible.

The effect would be to reduce gas pressure or make the gas supply erratic and unreliable. If it were happening, you'd probably be able to see the size of the burner flames get visibly and erratically smaller.

Again, not very likely but possible on some older kinds of gas distribution systems.
 
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Old 02-09-10, 10:07 AM
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Clicking has stopped once furnace fan starts running but it is still clicking quite a bit up until that point. Any ideas on what to do next?

Thanks very much for time and feedback, it is much appreciated!
 
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Old 02-09-10, 10:18 AM
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Having replaced the pilot switch and cleaned the pilot orifice, this still suggests to me a gas supply problem not allowing a sufficiently large pilot flame to keep the pilot switch hot enough to keep the main burner lit.

However, further analysis really calls for a repairman who can analyze and test what is going on, I'm afraid.
 
 

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