furnace question

I know some of ya'll will be all over this with good suggestions.

Got a gas lennox furnace,and its been doing this off and on for several years.It kicks on fine,works great,but the blower won't always go off once the temp. is reached and the burners go out.Sometimes it stops after a minute,but other times the blower will run an hour or all day.If it dosen't go off,I trip the circut breaker.Turn the breaker back on later...couple hours or days,sometimes the fan will be right back on,others it won't go till the burners fire up again.

I'm guessing there is some type of faulty sensor or relay.Pretty soon the extra elec. cost will equal a service call,which I'm trying to avoid.

Older gas central system,filters are clean,and I replaced the thermostat last year hoping that would fix it.It didn't:mad:

I would think your guess is right, sensor or relay malfunction, which? sorry I can't help.
My daughter had her furnace go out a few weeks ago when the temps dropped below 20 deg., really bad timing, but for the $65 dollars it cost to get a diagnosis it was worth it to find out it was kicking out very high carbon monoxide levels and to quit using it and replace it.
Not good news but very important to know what it is doing.

Cook I think "Sliles" or whatever his name is in that business but don't see him on here very often. If he's got one of them fancy phones he should get an e-mail alert on it if you send him a PM that he has a message on Crappie.com and possibly he will get on, check it and send you some advice.

Sam "Hookedonfishin" is a fitter but his company also handles that kind of thing so he might be able to guide you in the right direction.

Sorry, I can't be of any more help than that.

On mine there is a dial thermostat by the blower that kicks the blower on when the furnace has reached the temperature the dial thermostat is set at, and turns it off when it falls below it. Mine was just full of dust, blew it out and it was fine after that. Hope this helps.

ck filter if clogged replace other wise it's a bad fan control you didn't say model of lennox furnace . if below 80% efficent it's the fan control. if it's above 80 it;s the printed circuit board...

Rich is exactly right. I own a HVAC company. If there is an electronic control board in the unit the problem is a relay on the board. If this is the case, the whole board will have to go.. If there is no board, the fan limit, or cam stat is the problem...either of which is an easy fix.

Thanks,guys..I'll pull the cover and try to find these things later today(its only 330 am now)

Hope you got'er going alright......

I had that same issue a few years ago, furnace would run all day and blow cold air, wouldnt shut off unless i turned it off, called repair man and took two weeks to diagnose and fix, first time he said it was thermostat, replaced that, nope! didnt fix it, said it was the board and ordered that, nope didnt fix it!, came back over and took the cover off, used his screwdriver to tap on this and that, then took some rubber hose off and sucked on it like he was ciphoning gas from a car then blew in to and PRESTO! out comes some water,,furnace worked fine after that.

BUT I WAS SURE PI$$ED OFF!!:mad: took em two weeks to figure that out!!:eek:

Well,I poked around it,but its been pretty cold and 1 foot of snow on the ground..I ain't messing with it yet..still heats fine...runs enough now not to worry about the fan running a little extra.

Thanks all