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I have a Lennox 51M34 Merit Series programmable thermostat. It's currently set to 68 degrees, but it's maintaining a constant 64 degrees (as if that's what it's set to). The furnace comes on and goe

I have a Lennox 51M34 Merit Series programmable thermostat. It's currently set to 68 degrees, but it's maintaining a constant 64 degrees (as if that's what it's set to). The furnace comes on and goes off just like it's set to 64 degrees (it's not constantly running), even though it's actually set to 68 degrees. Setting it anything else (like 70 degrees) doesn't change anything--it wants to maintain a constant 64 degrees. Is this something that can be fixed/adjusted? Or does it sound like I need to replace the thermostat? Thanks!

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  • 2 Answers

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Posted on Jan 02, 2017

Sea Breeze
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SOURCE: Runs constantly to maintain 40 degrees, requires highest setting

Not sure how old it may be, but you can check a few things to see if it's defrosting properly. Also clean the condenser coils under the refrigerator to insure good circulation of air over coils. In the picture below you will need to check out three things until we find the problem. Defrost timer, defrost heater, and defrost thermostat. Let me know when your ready, Sea Breeze


Posted on Apr 20, 2009

  • 1 Answer

SOURCE: Lennox merit series furnace is not kicking on

I have the same issue with a G21Q4-5-100-1 model lennox. House drops 8 - 10 degrees. I have 3 thermostats and all react the same way. I was told by service tech that the Ignition Coontrol Module is bad and acting intermittanely. ???

Posted on Feb 16, 2010

  • 6826 Answers

SOURCE: temp setting way off kenmore 580

Remove the window unit and dissasemble,and clean it out,careful not to bend the fins on the condense and evaporator,but clean them out,and the inside of the unit also,then see what happens,if the problem persist,then find the probe on the evaporator and move it away from the evaporator until the compressor stays on longer.

Posted on May 27, 2010

  • 2272 Answers

SOURCE: Honeywell thermostat; Lennox elite series

When the furnace exceeds the temperature set by the thermostat, this could be indicative of several issues. The thermostat mounted crooked. When a thermostat isn't level on the wall, it can affect the automatic on/off function. To fix this problem, pop the cover off of the thermostat and loosen the screws attaching it to the wall. Straighten the device and tighten the screws.

If the thermostat is level and the temperature regulation system is still malfunctioning, the problem is most likely with the heat anticipator setting. The heat anticipator is a device inside the thermostat that governs when the furnace turns off. When the heat anticipator is on the fritz the furnace doesn't receive accurate direction, resulting in a heat system that either runs too long or not long enough. Usually, simply adjusting the heat anticipator, which is a small disc located underneath the thermostat cover, will fix this problem.

  • Temperature Does Not Reach or Exceeds Setting

  1. Thermostat is not level ? Use a level to realign thermostat.
  2. Anticipator not set correctly ? Adjust the anticipator.
  3. Thermostat not calibrated ? Recalibrate line voltage or low voltage thermostat.
  4. Range stop incorrect ? Clean thermostat and check .if same problem then,Replace thermostat.
  5. To clean thermostat.
  • Kill the power at the circuit breaker panel.
  • Remove the thermostat cover.
  • Clean the bimetal coil with a soft, clean brush.
  • Remove the thermostat body by unscrewing the retaining screws (on a round thermostat). Slide a piece of bond paper between the lever and contacts to clean them.
  • Reassemble the thermostat.

  • Thanks. keep updated for any more can rate this solution and show your appreciation.

    Posted on Sep 21, 2010

    • 1515 Answers

    SOURCE: Our Honeywell programmable thermostat is

    Good Morning, and yes you said it. Anytime a stat doesn't come on when it is set for a call for heat or cooling, the sensor on the subbase of the stat has lost its ability to sense the correct temperature. I have seen mechanical stats last as long as 25 plus years, but that's truly amazing for a digital stat to last that long. Yes, replace the thermostat. I don't know what kind of system you have, but if its a gas furnace with an a/c, the wiring will look like this. You will have terminals marked R, Red, for the 24 volt hot wire, G, Green, Y, Yellow, and W, White for heat. Going back to the red wire, it should have RC and RH on it. There will be a normally red wire connecting the 2 terminals.The Red wire coming in can connect to either one, as they are all together. The new stat will come with the new Red jumper wire attached. So, if you do have a gas heater, this is very easy to install. The only terminals you will need to use are RH to RC for the incoming red, Y, G, and W for heat. Y is for cool, and G is for fan. Very easy. Now if you have a heat-pump, they have many more terminals and can be a problem wiring them. If you have gas, forget the heat pump. I wont confuse you by going there. If it is a heat-pump, contact me in the comment box to let me know, and I can help you there also. Get a new stat at Home Depot, Lowe's Hardware, or O.S. Hardware. You want a 5 day, 2 day programmable Heating and cooling thermostat, 24 volts.It will have everything you need. See if it takes batteries for the display, they may not come with those, it will say on the box. Turn off your power to heater, so you won't short out the new one.They come in 2 sections, first the stat that just snaps on, and the subbase that is screwed to the wall. It will have the wiring terminals on it. Remove a couple of screws and loosen wires and remove. Be sure you write down how the wires go in case they used different colors, you never know. You will be all set. Store the manual in a safe place for future use. I wish you the best.
    A/C, Heating, & Refrigeration Contractor.
    PS, Please rate me on this :))
    Happy Holidays to you and family!

    Posted on Nov 23, 2010

    Testimonial: "I hate spending money needlessly replacing items that may not be the problem. Thank you for confirming my suspicions."

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    To keep your temperature at a single setting, just enter the temperature at every period, i.e. WAKE, LEAVE, RETURN AND SLEEP for both the Monday through Friday time frame and the same for the weekend. I do this at 55 degrees when I'm going to be out of town.
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