Gibson KG75A 054C 23A furnace - Only Works with Top Metal Cover Removed


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Old 11-06-10, 11:33 PM
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Question Gibson KG75A 054C 23A furnace - Only Works with Top Metal Cover Removed

Brand new unit - been doing it since it was installed. I rent an apartment so this is something my landlord is paying for and I have had the tech out twice now, first time he replaced the motor, second time the circuit board.

I have tested a lot, and it definitely only works with the cover removed, otherwise the flame comes on for about 5 or so seconds, then clicks off, repeats the procedure 3 times then trips the lockout (alternating green / red lights).

Before he gets too far into chasing the problem I wanted to see if anyone here had an idea I could suggest to him. I have searched around the net and seen a couple posts, some saying ignitor may be failing or out of place, others saying "sail switch" not closing, and another saying gas valve.

I work on computers for a living, not HVAC but I want to help the guy out from having to take time out of his schedule chasing down my problem.

Just to note, I had the cover off for a couple weeks, works great.. figured "okay time to put the cover back on" and the same night my problem came back. Cover off, been okay the last three nights - so I am 99% it is related to this cover doing something and as far as I can tell it is not hitting any wiring or the control board.

One last thing to mention, this thing constantly hums! installer said this is normal.

Thanks a lot guys!
 
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Old 11-07-10, 12:49 AM
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The furnace manual is available here:


http://www.grandaireac.com/Products/KG6RC_TS_828a.pdf


The symptoms you describe suggest that the furnace is shutting off because the circuit board isn't detecting that the burners are lit. Are you getting a diagnostic code that suggests that? If not, what diagnostic codes are you getting? Usually they'll be printed on a furnace label someplace.

This is a sealed combustion system, which would make it unlikely that the furnace cover is going to be able to influence the burner operation.

Your repairman should measure the flame rectification current going back to the circuit board to see if it's marginal which might indicate a problem. If so, cleaning the flame sensor and measuring the current to see if it changes would be worthwhile.

And I'd check the position of the flame sensor to make sure it's secure and in the burner flame pattern.
 
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Old 11-07-10, 10:42 AM
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Just to entertain your idea that its not the cover, after it working another two days with it off, I just went down and put it back on. Same thing.

That's 6 times, without fail, that taking the cover off makes it work, and putting it back on makes it fail - first go.

It cycles 4 or so times, then my red and green do an "alternating flash" signaling one hour lockout, which to me isnt a very good code to work with.
 
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Old 11-07-10, 11:40 AM
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I wonder if the rubber hose on the exhaust is getting mashed with the door. Kind of a long shot but worth looking at.
 
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Old 11-07-10, 11:42 AM
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Why post here if you are convinced you already know the problem?



When a piece of equipment is on the edge of failure, a lot of peculiar things might cause it to start to work, temporarily. When the problem gets worse it then quits working at all.


I recall a gas fireplace that had glass doors in front of it. The homeowner found that if he "flapped" the glass doors the fireplace would turn on! The real cause of the problem was a dirty pilot light.


I expect you have some problem which is causing the peculiar operation of your furnace --- it's not working the way the engineers designed it.

But if you want to pursue your own theories, help yourself.
 
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Old 11-07-10, 11:50 AM
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Who is convinced they know what the problem is? I just know how to recreate the problem, which is usually a good first step to determining the issue.

I am not pursuing any theories, simply seeking solutions! Did not mean to touch a nerve, I will just go ahead and let the tech who installed it take care of it - I thought these forums were here to help people not persecute them.


edit: I ran my hand around the whole area where the cover goes on, nothing seems to be near where it would be touching and I do not see any rubber hose near the door - and again just to be thorough tried twice each time again, with cover off and on - each time again - off it works, on it doesn't. The flame comes on then just goes out and the unit clicks after 10 seconds of it being on.

Thanks anyways guys - ill post back with whatever the solution ends up being.
 

Last edited by Mr.Breakit; 11-07-10 at 12:13 PM.
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Old 11-17-10, 01:09 PM
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Issue Resolved

One of the Cross sections in the venting had a piece of insulation stuffed into it as if when they were installing it they used it to temp fill the opening at the T in the pipe, but then someone closed it in.

With the cover on it was too clogged to turn the system on, with the cover off it must have allowed enough of the back flow to escape the open door and allow the system to turn on.

So anyone who has this bizarre problem.. check your vents for blockages!

Thanks everyone!
 
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Old 11-17-10, 01:34 PM
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Originally Posted by Mr.Breakit View Post
So anyone who has this bizarre problem.. check your vents for blockages!

It's pointless to try to solve problems by supposing some freak problem is the likely cause.

Good diagnostic methods are what is called for, which allows problems to be observed and then possible causes analyzed one by one until the problem(s) are discovered.

Your repairman obviously has limited skills considering the motor and circuit board he replaced without having isolated what was causing the burners to shut off.

What presumably WAS shutting the furnace off was the pressure switch opening due to the vent blockage. He probably should have been able to observe that, which should have led him to examine the heat exchanger and venting system, not the circuit board and such.

Indeed, I'd guess that's what he finally got around to noticing and which led him to inspect the vent for obstructions.

I'm sure you use similar diagnostic methods in tracking down computer problems. I would presume the logical methods have a lot in common even though applied in different ways.

Anyway, glad you got the problem fixed.
 
 

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