# Gas Furnace fails only at night - pressure issue?



## Ken321 (Apr 12, 2012)

*Hi – My gas furnace works during the day, but not overnight... Is this a gas pressure problem? Any help you can provide would be very much appreciated given I just wasted $150 on a service call.

Gas furnace cycles correctly during the day (including on/off based upon programmable thermostat). Blower kicks on, followed in a few seconds by "sparking" sound, followed by ignition of full burner set. While I can't see the lighting of the pilot, I'm pretty sure there is a quick ignition prior to the full set of burners lighting.

At night I hear the furnace trying to "start." Specifically, I have observed that the blower comes on for 3-10 (?) seconds, and then shuts down. No sparking sound. I've also observed with the lights out and see no flash of a spark. Subsequently, the cycle will start again in, say, 10 seconds, with no better results. I have observed this cycle lasting 10 minutes before I switch the unit off. I have never seen the unit either succeed or stop this cycle prior to my shutting it off. (As a sidebar, the manual says the ignition system will retry for 90 seconds to light the pilot, then shut down for five mins, and then retry two more times. I think this is immaterial, though, given it isn't even getting to the "sparking" step.

Despite searching, I can't find a list of reasons that the igniter would not fire which could be attributable to some kind of variable (not the on/off switch). So, my questions:

1) Is there a sensor that triggers the igniter to kick in or not? If so, what is it sensing?

2) Is it possible that I am receiving low gas pressure in the overnight hours? Also, my gas lantern light post seems to be well lit during this time. Before I call BGE, I'd like to know if it is a possibility. (I will also ask some neighbors if they are having similar problems.)*
*Many thanks in advance*


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## how (Feb 26, 2011)

Age/ brand & model of furnace would help.

Does this problem occur every night? I'm guessing you don't have a diagnostic led that could give you a fault code?

Given all the symptoms you've mentioned.....
I would first swap your progamable stat with a cheap thermostat to see if the inducer still only powers up for a few seconds at night.


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## COLDIRON (Mar 15, 2009)

Take the thermostat off programing for a couple days and see what happens. Just use it like a regular stat.


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## danpik (Sep 11, 2011)

I would agree with the prevoius posters to check the thermo. Are ther any other things that change between night and day such as a door to the furnace room getting closed?
It is entirely posible that there could be a pressure fluctuation from day to night depending on temperatures (Gets a lot colder at night) which causes moe gas usage at one time in the area. The gas company takes this into account when sizing gas mains for the area so, uless this has been an ongoing oroblem I doubt this could be the problem.

However, this is a problem we had once. durring a particullarly cold stretch of nights (-20 f) the pilot light on my furnace would go out each night. Thinking bad Thermocouple I replaced it. No luck, Still had the same problem. One day my wife noticed one of the local heating companies next door. she asked our neighbor what was up and she said they were having a problem with their furnace doing the same thing as ours. A call to the gas company yielded no results.problem went away once the nights warmed up some. Fast forward about 4 months. Saw a buddy who was working a dig site a few blocks from my house. His company was contracted by the gas co to do some gas line work in the area. They were pumping water from a hole they had opened up. Thinking broken water line I asked him what happened. They were tying into a gas main and found it full of water. They figure they pumped roughly 10,000 gallons of water out of the line when all was said and done. This was what was cousing the problem with the furnaces in my area and as I found out later several others in the area. The water took up so much volume in the pipe that when everyones furnace was trying to keep up with the cold the gas flow was not enough which caused furnaces to go out. 

Yes, they did find the leak that was allowing the water into the line a few days later


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## carmon (May 8, 2010)

I have to agree with the stat suggestion... try a new one if you can borrow one or take it of the program mode....


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## COLDIRON (Mar 15, 2009)

The thermostat is the first step. After that we move on. Step by step.


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