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mhill · Dec 9, 2008, 03:13 PM

I have an old (17 years) gas furnace that sometimes will not come on. It will start, the burners will light up but they will shut back down after about 10 seconds. It will repeat this cycle several times and then it will shut itself off. This cycle appears to be random as it only happens some times. My repairman said there are a couple of potential causes that I don't really have money to fix right now, but he also suggested I replace my Maple Chase thermostat as he said he has more problems with that brand than any other. The thermostat is about 10 years old. It's the kind that is programmable and it has a button for Heat/Off/Cool and a fan button for Auto/On.

My question - can I replace this with a Honeywell 5/2 programmable thermostat? Is there anything in particular I need to look for in a thermostat to ensure it will work with my old furnace? I no longer have the owner's manual and I'm not at home right now so I don't know the brand/model of my furnace but like I said it is 17 years old. Also my repairman said this is an easy thing to replace and I should be able to replace myself without any problems - do you agree? Any info is appreciated. - Michelle

hvac1000 · Dec 9, 2008, 04:29 PM

Originally Posted by mhill

I have an old (17 years) gas furnace that sometimes will not come on. It will start, the burners will light up but they will shut back down after about 10 seconds. It will repeat this cycle several times and then it will shut itself off. This cycle appears to be random as it only happens some times. My repairman said there are a couple of potential causes that I don't really have money to fix right now, but he also suggested I replace my Maple Chase thermostat as he said he has more problems with that brand than any other. The thermostat is about 10 years old. It's the kind that is programmable and it has a button for Heat/Off/Cool and a fan button for Auto/On.

My question - can I replace this with a Honeywell 5/2 programmable thermostat? Is there anything in particular I need to look for in a thermostat to ensure it will work with my old furnace? I no longer have the owner's manual and I'm not at home right now so I don't know the brand/model of my furnace but like I said it is 17 years old. Also my repairman said this is an easy thing to replace and I should be able to replace myself without any problems - do you agree? Any info is appreciated. - Michelle

Do this first. Clean the flame sensor if equipped with one. Fix the furnace first then replace the thermostst.

mhill · Dec 9, 2008, 04:55 PM

Do I need to shut the power off at the circuit breaker to clean the flame sensor or do I just turn off the power switch inside the furnace closet, or do I not worry about the power?

By the way (if this matters at all), I've been having this problem with the furnace for the last two winters and my repairman has been able to keep it going with just maintenance; we haven't replaced anything yet. This morning was the first time so far this winter that the furnace started doing the "switch off" thing again. It usually doesn't do it on the first run (when there is a big temperature difference between the room and the thermostat setting), it usually happens when it's only a few degrees difference between air and setting. Let me know about the electricity being on or off.

Thanks,
Michelle

hvac1000 · Dec 9, 2008, 05:27 PM

Power switch will work. You do not want the furnace to come on while you are doing it. Becareful around the ignitor(the thing that glows) it is sensitive so do not touch that part.