Furnace/burner problem

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  #1  
Old 12-01-02, 12:00 PM
rgmess
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Unhappy Furnace/burner problem

Got a Carrier 58GSC080-DB Series 110, 1987 forced air unit. Uses a White-Rodgers 36E gas valve. Problem: pilot lites OK when turn heat on at thermostat. After a minute or two the gas valve clicks and as soon as the burners lite, they go out. They are on for less than the time it takes for the flame to travel all the way down the burner, then everything shuts down, and after a moment the pilot tries to lite again (unsuccessfully). When I turn the tstat off, then on again (for heat) this process happens again. Have jumped the red/white wires at the tstat and same problem. Haven't seen quite this problem in the forum, so am posting. Any help? Thanks.
 
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  #2  
Old 12-01-02, 12:08 PM
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what kind

of ignition does it have? pilot always on, spark lights pilot or hot surface?
 
  #3  
Old 12-01-02, 10:52 PM
rgmess
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Spark lights pilot. Seems to work well, lights it fairly quickly. Takes approximately 2+ minutes between when the pilot lights and when the burners finally try to light (and immediately shut down).
 
  #4  
Old 12-02-02, 05:48 AM
rclhvac
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Pilot oriface is dirty & causing the pilot not to burn properly.
If it is a #733 pilot assembly- they have a newer one # 740
 
  #5  
Old 12-02-02, 09:09 AM
rgmess
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Thanks, I'll check that out. Out of curiousity, how does that cause the problem I am having?

-- Randy
 
  #6  
Old 12-02-02, 12:03 PM
rclhvac
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The flame is supposed to go in 2 directions - 1 towards burners & other to bimetal switch. When dirty it floats away from the bimetal. After cleaning or replacing you will see & hear the difference
 
  #7  
Old 12-04-02, 01:09 PM
rgmess
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Checked it and the flame is being split and hitting the bimetal. Cleaned it as best as possible but still the same problem. Will replace it and see what happens. BTW, it is a 740. Spark shuts off fairly soon after the pilot lights -- I assume that is a result of the flame detection on the part of the bimetal?

-- Randy
 
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Old 12-05-02, 06:49 PM
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pilot burner

is what carrier calls it. determine if it is 2 or 3 wire. replace it.
 
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Old 12-05-02, 11:34 PM
rgmess
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On the road to replacement and will post the results. Thanks.
 
  #10  
Old 12-06-02, 03:02 AM
cyberexec
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Have you checked your fan motor?

Rg...does your fan come on. The gas will shut off to the burners if the fan does not come on. I recently had a problem like yours, and ended up replacing my motor to resolve my problem. You can read my previous posts regarding my problem with my furnace to see if they are any help to you. By the way I am a novice at gas furnaces, and this was my first attempt to fix my 15 plus year old furnace. The guys here and the diy'ers are great, and helped me out with my questions. Hope this info helps you in some way.
 
  #11  
Old 12-06-02, 01:36 PM
bigjohn
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When the pilot flame ignites, the module has a current path to ground thru the flame signalling the module to shut off the spark. The pilot flame heats the bimetal switch which, when it closes, allows the gas valve to open and ignite the main burners. My experience has been that the bimetal switch is one of the most common failure parts on a Carrier.
 
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Old 12-06-02, 04:54 PM
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gas

If you have a gas pressure gauge, check the inlet and outlet gas pressure. I think you'll find your not getting the 3.5"WC of gas on the outlet side. Make sure you check the inlet side as well, it should be 5 to 7"WC before and during firing. Pilot burners are the common problem on Carrier, Bryant and BDP units.
PS these pressure are for Natural gas only.Do you have LP or natural gas?
 
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Old 12-06-02, 05:12 PM
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Rollout

Have you looked to see if there is a rollout switch in the schematic?
 
  #14  
Old 12-15-02, 03:18 PM
rgmess
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Thanks much to all. Finally found a new pilot burner and installed it. Did the trick. While I was waiting for the new part I fiddled with the old one. Am curious what it does exactly. I noticed that there are two adjusting screws that allow you to adjust when contact is made during the bimetal heating phase. Looks like it can be set so that there is a delay between when one of the switches makes contact and when the other does. (It's a three-wire switch). Can anyone tell me how the switch is supposed to operate and what each switch contact controls?

-rgmess
 
  #15  
Old 12-15-02, 03:51 PM
rclhvac
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Normally closed (cold position) completes pilot circuit. When pilot lites it warps to normally open side to close contacts to complete circuit for main burner
 
  #16  
Old 12-15-02, 07:36 PM
rgmess
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Thanks Rick. The implication is that when the circuit finally closes for the main burner, the pilot circuit then goes "open" -- would this turn the pilot off once the burner's are lit, or once it is on it stays on?
 
  #17  
Old 12-16-02, 04:24 AM
rclhvac
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It stays on to keep switch closed for the gas valve. The valve is a redundant (100% shut off) and closes as soon as the 24v is removed. Then the pilot has to cool down to start over again .
 
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Old 12-23-08, 07:59 AM
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Where can I purchase a three-wire pilot (732, 733, 740)?

Originally Posted by rclhvac View Post
Pilot oriface is dirty & causing the pilot not to burn properly.
If it is a #733 pilot assembly- they have a newer one # 740
I'm looking for a source for a three-wire pilot - I'm not a lic. contractor, so having trouble finding a shop that will sell a 732/733/740 pilot assembly.
Thanks!
-Bill
 
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Old 12-23-08, 05:48 PM
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pilot assy's

are you kidding? There are tons of places online...do a search on Google...
 
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