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    senada's Avatar
    senada Posts: 4, Reputation: 1
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    #1

    Nov 19, 2006, 01:40 PM
    Thermostat problems or furnace problems
    Is it possible that a thermostat operates correct all the time except when it reaches the temperature that is set doesn't maintain that temperature?:D
    I noticed that actually that thermostat gives a signal to the furnace but furnace doesn't turn on but that happens only when thermostat needs to maintain temperature that is set.
    Is it possible that thermostat isn't working at that regime (to hold the set temperature)?
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
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    #2

    Nov 19, 2006, 02:25 PM
    The thermostat is simply an on/off switch. Below a certain temperature it is on. That will turn the furnace on, and heat up the house. Once it gets above the set temperature, the switch opens and shuts the furnace off. It has a little bit of a dead area so that it isn't constantly turning on and off. That can be adjusted. The older ones that relied on a bimetal spring and mercury tilt switch wouldn't work right if not level. Round ones are difficult to get level. Newer electronic thermostats can have other problems.
    gautamanne's Avatar
    gautamanne Posts: 9, Reputation: 2
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    #3

    Nov 19, 2006, 05:04 PM
    I think its your thermostat.. See if you can go to your local Home Depot and get a Rite Temp thermostat and call the RiteTemp hotline and have them help you install. Ask for this dude called david. I had a similar problem and was able to isolate by calling these folks.. Otherwise would have costed me a lot to call the tech.
    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
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    #4

    Nov 19, 2006, 09:37 PM
    Is this a digital stat? Could there be a heating temperature differential you can change in the user set-up? Is the W wire hooked up to W2 ?
    senada's Avatar
    senada Posts: 4, Reputation: 1
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    #5

    Nov 20, 2006, 09:10 PM
    Yes it's digital, but there is no w2 position only w. Anyway I changed thermostat today and will see how it works.
    senada's Avatar
    senada Posts: 4, Reputation: 1
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    #6

    Nov 21, 2006, 07:53 PM
    Now I know it's not thermostat. Furnace still acts same. Any suggestions what could be a problem. Furnace is 7 years old & it's Lennox G20.
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
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    #7

    Nov 21, 2006, 08:28 PM
    I still don't quite understand the problem. If the furnace and thermostat are working properly, the heat will cycle up and down. When the furnace is on, it heats faster than the house loses heat. When it gets up to a point, the thermostat turns it off. Then the house loses heat until cool enough for the thermostat to turn the furnace back on. If the range is too great, Northern Heat and I both mentioned adjusting it.
    senada's Avatar
    senada Posts: 4, Reputation: 1
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    #8

    Nov 21, 2006, 09:49 PM
    What's happening is that furnace fail to start every time when it reaches set temperature.
    It works like this: thermostat gives a signal to start furnace, damper door opens, LED lights turns on, pilot flame shows up, LED light turns off, dumper door remains open, furnace not working. Furnace will never start working even when temperature drops for couple degrees unless I turn off/on furnace on power switch.
    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
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    #9

    Nov 21, 2006, 09:54 PM
    OK lets start over. What brand, type, age and efficiency furnace/boiler/heatpump do you have?
    simshawk's Avatar
    simshawk Posts: 3, Reputation: 1
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    #10

    Dec 3, 2006, 02:22 PM
    Quote Originally Posted by senada
    Is it possible that a thermostat operates correct all the time except when it reaches the temperature that is set doesn't maintain that temperature?:D
    I noticed that actually that thermostat gives a signal to the furnace but furnace doesn't turn on but that happens only when thermostat needs to maintain temperature that is set.
    Is it possible that thermostat isn't working at that regime (to hold the set temperature)?
    I just posted a similar problem today with the LED displays (User ID: simshawk). My unit is a Lennox Elite Surelight, 6 years old, Nat Gas, using a ritetemp thermostat.

    When the desired preset is met, the unit kicks off and will not restart until I perform a manual reset.

    Here is my post:

    Having the following problem.

    Woke this morning and temp in house was 62degs. Check thermostat and it said heating, temp set on 68.

    Checked the unit and the diagnostic LEDs were flashing alternatively and slow. According to the Diag Sheet, this is "Watchguard - Burners failed to Ignite".

    Shut unit down and waited 15mins, performed a restart and unit was working properly, both LEDs flashing simultaneously and slow.

    Temp got to preset value 71 degress and the unit shut down again. Noticed temp went back to about 67 degrees, thermostat was showing heating, but nothing was coming from the vents, and no flame on the unit.

    Check LEDs again and saw the same "Watchguard" failure as above. Shutdown unit and performed a restart, heater kicked on, but now the LEDs are #1 slow flash, and #2 fast flash, which according to the status table is "Low flame signal, check flame sensor".

    Help, its going to be really cold tonight in MI.

    Jerry
    NorthernHeat's Avatar
    NorthernHeat Posts: 1,455, Reputation: 132
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    #11

    Dec 5, 2006, 02:40 PM
    Quote Originally Posted by simshawk
    I just posted a similar problem today with the LED displays (User ID: simshawk). My unit is a Lennox Elite Surelight, 6 years old, Nat Gas, using a ritetemp thermostat.

    When the desired preset is met, the unit kicks off and will not restart until I perform a manual reset.

    Here is my post:

    Having the following problem.

    Woke this morning and temp in house was 62degs. Check thermostat and it said heating, temp set on 68.

    Checked the unit and the diagnostic LEDs were flashing alternatively and slow. According to the Diag Sheet, this is "Watchguard - Burners failed to Ignite".

    Shut unit down and waited 15mins, performed a restart and unit was working properly, both LEDs flashing simultaneously and slow.

    Temp got to preset value 71 degress and the unit shut down again. Noticed temp went back to about 67 degrees, thermostat was showing heating, but nothing was coming from the vents, and no flame on the unit.

    Check LEDs again and saw the same "Watchguard" failure as above. Shutdown unit and performed a restart, heater kicked on, but now the LEDs are #1 slow flash, and #2 fast flash, which according to the status table is "Low flame signal, check flame sensor".

    Help, its going to be really cold tonite in MI.

    Jerry
    Clean the flame sensor, a small metal rod that is in front of one of the burners
    Cold in Canada's Avatar
    Cold in Canada Posts: 9, Reputation: 1
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    #12

    Jan 10, 2007, 12:06 AM
    Hi, I have the same problem as Senada, Simshak, and JS16. First my info I guess:

    Lennox Whisper Heat G20

    7yrs old

    80% Efficiency

    Forced Air furnace

    NG

    Digital Stat (Honeywell if it matters)

    Seems like the furnace doesn't want to go through a full cycle. The stat requests heat, the furnace lights up, it works for a while, and then shuts down refusing to start until a manual off/on procedure is carried out. Sometimes it works till the desired heat is achieved, other times it just cuts out randomly as if it were bored or tired of doing its job. It dies with the damper open, and a led on the ignition control flashing rapidly.
    A little history here is the furnace was doing the same thing last year so I called in a "professional" to see if he could fix it. After telling him what it was doing he put it through the paces. He removed the covers, and bypassed the safety controls then fired it up checking the pilot light, the burners, the stat etc. After an hour or more of this he finally declared " your problem is that the furnace shuts off and won't fire back up again and that little light on the board flashes off and on"... um thanks tips. After much head scratching and a few hmmsss and ahhhs he concluded that the only possible fix would be to replace the motherboard on the furnace. A few hours and $327.17 later and the furnace worked sort of. Now instead of shutting down early the little furnace was sure to reach the desired heat and then shut off, led flashing, refusing to reignite until the manual off/on cycle was repeated. My battle with him continues but that is another story.

    Now we are in back in furnace season and it has decided to shutoff as it feels again. Sometimes reaching full heat, and sometimes shutting down early, but always refusing to reignite, with that damn led flashing. I haven't noticed a regular pattern in the temp it shuts down at, but I did notice that our friend the led has learned a new trick. Now instead of flashing rapidly as if trying to emulate a strobe light, sometimes it chooses to flash at a slower rate (perhaps its getting tired from flashing so much).

    I located the flame sensor you mentioned, and managed to gain access to it (sort of) by removing a panel on the damper without damaging anything. It doesn't seem to be dirty, but before I go and do something stupid, perhaps you could tell me how to clean it ie: will household cleaners hurt it or make it dirtier?? soap and water?? no water as it could corrode wire? etc. Or is there possibly something else? Maybe we should change the motherboard again? If that is the case I think I'll buy a new furnace, I can handle spending the $20 bucks for a new filter each year, but shelling out over $300 every year on a new motherboard is a bit much. Hope you can help, and thanks in advance.

    CiC
    h-man's Avatar
    h-man Posts: 12, Reputation: 1
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    #13

    Feb 8, 2007, 02:49 PM
    Comment on NorthernHeat's post
    Short and to the point
    h-man's Avatar
    h-man Posts: 12, Reputation: 1
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    #14

    Feb 8, 2007, 03:09 PM
    Had a similar problem...

    House was very cold; could not maintain temperature.

    Gas furnace would reach set point, shut off, and then not turn on again.

    Only way to fire heater (Goodman) was to manually reset thermostat.

    Unit would heat to setpoint then stop working again.

    Tested thermostat; appeared to work fine.

    Located flame sensor and lightly cleaned with sand paper.

    Furnace working perfectly now.

    Many thanks to everyone (and this web site) for their help! :D
    PASSERVE's Avatar
    PASSERVE Posts: 9, Reputation: 1
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    #15

    Dec 13, 2008, 05:45 PM

    Clen the flame sensorwith some steel wool or small wire brush
    wmproop's Avatar
    wmproop Posts: 3,749, Reputation: 91
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    #16

    Dec 13, 2008, 09:55 PM

    These 2 year old post are popping up, are they helping someone ?
    imcintyr's Avatar
    imcintyr Posts: 1, Reputation: 1
    New Member
     
    #17

    Dec 15, 2008, 08:04 PM
    Quote Originally Posted by wmproop View Post
    these 2 year old post are popping up ,,are they helping someone ?
    I'm headed down to scrub my flame sensor so we'll see if they are helping... I'll report back when my house is warmer ;) It's 0F in Denver right now so I'm crossing my fingers.
    dpepsi's Avatar
    dpepsi Posts: 1, Reputation: 1
    New Member
     
    #18

    Dec 28, 2009, 10:37 PM
    Help me! 12-28-09 light sandpaper of sensor. Warm again! Thanks!
    slanwar's Avatar
    slanwar Posts: 1, Reputation: 1
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    #19

    Jan 30, 2010, 10:00 AM
    Well I had the same problem and I cleaned the flame sensor and worked for a few weeks, now is back with the same problem even after I cleaned the sensor again. I need to turn off/on my thermostat to kick in but then will not turn on again after (almost) reached the temperature set on my thermostat.
    mkelly5686's Avatar
    mkelly5686 Posts: 1, Reputation: 1
    New Member
     
    #20

    May 30, 2012, 09:51 AM
    I can no longer adjust the temp on my thermostat. The fan can be turned off or on, the air does come on. Please tell me I just need to replace the thermostat.

    Kate

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