Gas furnace burners turning off and on : LUSENET : Freedom! self reliance : One Thread

I have a mid-efficiency Comfortmaker gas furnace - 2 1/2 years old. It's been working fine up until a couple of weeks ago. Now while the furnace is running, the burners will go out for a second or two, and then light back up again. It doesn't happen every time the furnace runs - only every now and then, although it is starting to happen more often. When it does happen, it occurs the whole time the furnace is running - the burners go off and on, off and on, off and on until the furnace turns off.

I change the filter regularly and have just had the furnace cleaned. The thermostat is a Lux 500 programmable, and seems to work fine - turning on and off at the appropriate room temperature.

Any suggestions on this would be highly appreciated!! Thanks

-- jean luce (, February 14, 2004


Jean! Wow!! Sounds to me like the furnace is "hittin the limit". Assumin the t-stat is workin properly about the only thing left [except the blower] is the limit. When heat builds up to excessive amounts inside the furnace the limit temp will be achieved and will break the heating cycle. Nuther words---if your high limit is set at 180f [for example] and your blower can't cool the furnace down enough by distributing the warm air then this temp will soon build up to the 180f and open the heating circuit.

I am familiar with the Comfort Maker line of furnaces and they are a good'n. I don't know which model you have but probably wouldn't know anyhow if it has a mechanical fan/limit switch or if it's got the puter [ignition module] that controls the fire and blower. If it's the puter model you may have an adjustment on the puter board that allows you to change the settings of the "fan on" and "fan off" and "limit". I wouldn't change the Limit setting--just lower the "fan on" temp a mite. 5f is enough to start with.

If you have the mechanical switch--it will be located just about the burners and will have several wires runnin to it. Check the little round dial and locate where the pointers are at. Hold the dial [don't let it turn] and move the ''fan on'' down a mite.

Could be that the fan/limit/ switch [if mechanical] was faulty from the factory. Lowes, home depot usually has'm for about $20 or so. If it's a puter board--they are about $70 or so--wholesale and you'll have to go to a heating contractor probably to get one.

Another thing it can be is the blower motor itself. It may not be turning at the proper speed. If you have a/ca try switchin the blower lead from the 'slow' to the 'med' or even 'high'. AC's are run on 'hi'. Cold aire is harder to move than warm. Besides that when movin warm aire faster it'll cool it off some. Be careful workin around the limits. They carry 120 volts-- let us all know how it works out. I'll be gone this comin week and off line but will check back in next weekend. old hoot. Matt.24:44

-- oldhootgibson (, February 14, 2004.

I have the same problem but with an 18 year old Olsen furnace. Direct Energy (my service in Toronto, Canada) after 4 visits (changing the thermostats twice) said that the furnace is cycling on limit and has shut the gas off/furnace off. Their answer: get a new furnace.

It has been really hard to get a clear answer as to why the furnace would cycle on and off only once the temperature in the house was more or less at the thermostat temperature. The main answer has been that these Olsens have a real problem with overheating and the problem likely is holes in the secondary heat exchanger.

I know this isn't an answer, but could my problem be like yours? Could oldhootgibson's suggestions be relevant for my problem?

Thanks for any help.

Katherine Teide

-- Katherine Tiede (, April 30, 2004.

Hey Kate! If your furnace is shuttin down because it's hittin the high limit--. Some things that causes that--A faulty limit switch. A blower that's not movin enough air to take the heat from the furnace. a faulty fan switch.

Now I'm afix'n to tell you some things you can do to check it out. I'm not familiar with the Olsen furnace but most of'm are basically the same. With the POWER OFF install a jumper across both terminals of the limit switch. Turn on the power and see if it will run without cyclin. If it does--faulty limit switch. If not--try jumperin the fan switch so the blower will run comntinously. If the fire continues to burn--faulty fan switch, faulty blower motor.

The T-stat doesn't have anything to do with the fire shuttin off UNLESS the heat anticipator is adjusted wrong. This HA is located inside the t-stat and needs to be set to match the amp ratin stamped on the side of the gas valve. Usually about .4 or so. The furnace will short cycle if it's set too high--run longer than need be if it's too low.

Hope this has helped ya'll out a mite Katie! Oh BTW--my wife is named Kathryn. I call'r "lil dumplin" since she don't like bein called "katie"! Lol. Let me know how things go. Please be careful when workin around these controls. Some of'm are 120 volts whilst some are only 24 volts. old hoot. Matt. 24:44

-- oldhootgibson (, April 30, 2004.

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