Sporadic burner won't light

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Old 12-14-07, 05:42 AM
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Sporadic burner won't light

Hello;

I have a Carrier Weathermaker 58SXCo80-JG furnace, 15 years old, with electronic ignitor ignition. This is a natural gas furnace. Sporadically, it will get a call for heat and cycle but won't light the main burner. It attempts this 3 times then "locks out" and shuts down. It has a White-Rogers 36E gas valve. I replaced the main board on this furnace last year.

When I observe the cycle, everything is occuring in the proper sequence. When the ignitor lights I can hear the main gas valve solenoid "click" but no gas gets through to the main burners. If I "tap" on one of the solenoids on top of the gas valve, I can get the gas to flow and the burners to light. The furnace will then work fine for a period of time until this phenomonon occurs again. Sometimes for days, sometimes 6-8 hours.

Any help would be greatly appreciated.
 

Last edited by Herbietim; 12-14-07 at 05:44 AM. Reason: addition
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Old 12-14-07, 08:29 AM
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Sounds like the gas valve, and you probably already suspect that since you know that when you tap on it it comes on. Have you only recently had the furnace running now for the season?, or is this a problem that has developed suddenly, well into your heating season? The reason I ask is maybe if you have just started to use the furnace this stickiness might go away. Might, if it is sticky.


I have a furnace in a rental right now that is behaving the same way and is VERY sporadic and I myself am not sure if it's the ignition module (it sparks, but not he world's largest), bad plug wire (as it had been shorting to the sheetmetal), dirty electrode, gas obstruction or sticky valve once in a while. I check on it daily ( a not-out-of-my-way-rental) to see if the bugaboos are working themselves out, the more the furnace has to run, as this problem became noticed from the first day of the heating season (it's in a very cold furnace room), and am hoping now that it has to run more, everything will loosen up better. You have to pull the valve/burner to service any of the components I listed, and don't want to do that if the problem works itself out. It was 2 below this morning and it was running.
 
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Old 12-14-07, 08:45 AM
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Thanks for the reply. No this has been going on since last year. The furnace serviceman replaced the main board last year and teh unit seemd to work ok for a while. However, we had the same problem at the tail end of the season last year and now since the start of the season this year.

I am now skeptical that the $600 I spent last year was well spent.

Is there a way to open the valve up to see if the main valve can be lubricated or? I've never opened on and was a little afraid of removing the screws and finding that everything falls out of place.
 
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Old 12-14-07, 01:42 PM
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Never open up a gas valve. You open yourself up to some real possible legal issues if you do. You should only do that if yours has been removed and a new one installed and you are merely curious about how they work inside. Lubricant is out of the question as that attracts dirt.

Sporadic furnace troubles can be tough to diagnose because if it is working at the time, a test meter across electrical connections will read good at that moment.

Chances are that if your ventor is just running and you have no heat, that the unit has made 3 attempts to light and failed and has gone into lockout mode. And the reason it did is because ignition was poor, gas to the ignition area is poor, a bad ground, diversion of spark or weak HSI (depending on what you have), a bad igniton control module, a weak borderline pressure switch, or a borderline furnace drafting issue, or one of the various relays has contact points that are getting bad inside, and one minute make good contact and the next minute they don't.

If you were real lucky, there could be tarnished spade connectors and you could remove the connections and reinsert to make good contact.
 
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Old 12-14-07, 07:06 PM
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Thanks - I suspected as much about the gas valve. I have cleaned the spade connectors and all works the same as before. My ignitor glows very strong and never fails to light the burners immediately when the gas reaches it, so I t hink that is OK. I suspect one of the relays has a problem or the valve is "sticky" since it without fail will light if I tap lightly on the relay located on the right side topside of the gas valve.

So, I suspect then that the whole gas valve has to be replaced - correct? Is that difficult to do?
 
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Old 12-15-07, 03:23 PM
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Not for anyone who is used to plumbing and how tight to tighten things and using correct sealant, and is not afraid of being responsible about what gas can do.
 
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Old 12-18-07, 05:16 AM
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What would the best source be to purchase a new gas valve? Now the burners are sporadically lighting and going out after a minute or two.

It's time to do something.
 
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Old 12-18-07, 11:03 AM
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I am always hesitant to tell people on this board they have to go out and buy one of the more pricey components, out of fear it could be something simple, instead.

I have recently worked on a furnace with problems similar to you. You have to keep in mind that by banging on the metal valve, that you are also probably sending little shock waves through everything connected to it. This could be misleading.

The furnace I worked on had electronic spark ignition. It was doing all kinds of things. Running, not running, going out in 1 minute, going out in 5 seconds, etc. I ended up disconnecting the gas valve and pulling out the burner where there are 3 electrodes in all: The direct sparker (no pilot), the ground electrode, and the flame sensor rod. I brightened up all the rods, used emory and a wire tooth brush on parts, because all the conections that went back to ground were rusty. In fact, if the problem happens again, I am removing the rusted screws that hold the halves together and redoing these with new screws and brightening up the metal inbetween the halves, to make a more sure ground path.

If you look for a new gas valve you can try a mechanical supply house that deals in your make and tell them you will set up an account with them, if otherwise they won't sell to you.
 
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