weatherking 80PJ 2 out of 5 burners light


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Old 03-07-10, 07:11 AM
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weatherking 80PJ 2 out of 5 burners light

I have a 7 y/o weateherking 80PJ forced air 125000btu furnace recently only 2 of the 5 burners would light up. This is what happens:
1-the tstat calls for heat - good
2-the vent blower starts -good
3-the HSI ignitor glows - good
4 -gas valve opens (hear the click) - good
5-the first 2 burners ignite / blower motor comes on - good
6- burners shut down - bad
7- blower finishes cycle furnace shuts down - bad

I have cleaned the flame sensor and the limit sensors. No luck.
When i took off and reinstalled what I believe are called " in shot burners":from http://www.apiofnhanddeltat.com/link...6_478_rev5.pdf
I cleaned the orfices in the gas manifold. It fired up all burners. That lasted a couple of weeks.
I was wondering if the HSI could be bad - I had a similar problem with my stove the HSI would glow but didnt open the gas valve fully causing a loner preheat time.
I am thinking the HSI isnt opening the gas valve all the way not pushing gas to all the burners.
I am going to re inspect and clean all parts again -any advise would be appreciated.
Thanks Ray
 
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Old 03-07-10, 07:31 AM
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The gas burners fire off a manifold with a gas pressure common to all.


The HSI's only function is to light the gas. It's doing that, so it's not the problem.

The usual reason why a burner wont light is that it's dirty, usually the carryover ports which allow the flame to move from burner to burner. These are smaller than the main flames, and more like to get dirty. It's a 90% probability that cleaning the burners will solve the problem if dont properly.

Most inshot burners don't have a primary air shutter, which means that can't get out of adjustment m--- is that the case on your furnace?

Since cleaning the burner orifices temporarily solved the problem, I'd do that again, and check carefully for any debris that might be restricting or interfering with the gas flow.
 
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Old 03-07-10, 10:21 AM
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could be cracked heat exchanger, or maybe the inducer fan motor isnt sitting right or has come loose
 
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Old 03-07-10, 12:24 PM
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Adding to what SP suggests(which you need to do) - just to satisfy perhaps your curiousity - cleaning the flame sensor is a good idea anyway. But you need fire in the burners (that currently aren't lighting) to make the flame sensor sense flame. Hence the furnace shuts back down.
 
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Old 03-09-10, 05:27 PM
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Thanks for the info
SP your correct with the non adjustable burner. I took every thing out and noticed a little rust between burner 2 & 3 then a little more between 4 & 5 cleaned them up good with steel wool Cleaned up the flame sensor & checked all the screws to fans /blowers etc. The screws that held the burner down seemed a little loose - I got a turn or 2 out of some of them.
So the the HSI does not open the gas valve??
From what Ive read around I thought that current is sent to the HSI gets satistfied glows and opens the gas valve . Also that the HSIs sometimes get a hairline crack in them unable to be seen by eye but the HSI will still glow get a current reading and have enough to open a valve but not all the way.
Anyway I cleaned the s#!t out of the parts - kicker is it warmed up here and had to put the heat up to 70 to kick it on all worked. Not hoping for anymore cold weather but would like to see if this fixed my problem.
 
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Old 03-09-10, 06:38 PM
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On furnaces with a separate flame sensor, the only function of the HSI is to light the gas. The power to the HSI is switched on by a timing circuit for a certain number of seconds, and the the gas valve is turned on by a separate circuit and the HSI shuts off on the timer.

If the burners light properly, the flame sensor detects that fact and leaves the gas on. If the burners don't light correctly, the flame sensor circuit shuts the main burner gas off after three seconds or so.
 
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Old 03-10-10, 05:36 PM
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Burners

Between each of the burners (on the flame end) is a small slot. These slots are the carryover ports SP refered to. Remove the burner assembly, clean those slots & blow them out with the canned air you use on the computer keyboard. A blade type feeler gauge works well for cleaning.
 
 

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