My furnace doesn't turn on even when the setting falls below what is on the thermostat.?

This doesn%26#039;t occur all the time, but occurs more often when it is very cold outside. For example, if I have it set at 71, the temperature in the house often falls into the 60%26#039;s overnight. In the morning I must manually lower and then raise the thermostat in order to get the furnace to kick on. I have changed thermostats, so I know it isn%26#039;t the problem.|||here is a link to troubleshooting a gas furnace. http://home.howstuffworks.com/how-to-rep鈥?/a> if the unit had not been serviced in a while, consider getting it done|||Have you checked the safety cutout switch that is activated when you remove covers to clean the filter? If you don%26#039;t get the cover(s) back on properly the cutout switch might be the problem.





However, the characteristic of working by manually lowering and then raising the thermostat does not fit this very well. That kind of sounds like you could have a relay contact in the furnace control that is faulty.|||It sounds like the unit is locking out and you are reseting it. Before you reset it go to the unit and look at the red light. Count the flashes and then check the chart to see what the possible causes are. Then you can check out the troubleshooting guide on the furnace page at my source to narrow it down.|||It does sound like the thermostat system is faulty. Make sure the thermostat you installed is compatible to your heating system. Cheapest does not mean it works all the time. If it is, you may want to try loosening the thermostat wires at the furnace and re-tighten them. Also make sure thermostat wiring is not making connection with other wires or metal casings. (inside the thermostat too)|||He already said he changed the thermostat. Its most likey a bad thermocouple.|||two possible things..bad thermostat or thermo senser...or a bad regulater that tells the furnace to come on or go off...is this a gas or electric ???|||If it has a little mercury switch inside it, the thermostat needs to be leveled when installed on the wall, or this exact result can happen.


It could also be the relay switch on the furnace itself, not getting the signal from the thermostat.|||Sometimes this can be caused by a bad splice in the thermostat wiring. If you have an ohmmeter, you could disconnect at both ends, twist together at one end, then measure the resistance at the other. It should be very close to zero.|||If this ONLY happens at night, your pressure switch inside the unit could be faulty. This is the switch that monitors the exhaust motor to come on and of. If there is a dramatic difference in humidity outside, from day to night, moisture settles in this switch from the exhaust vent pipe through th attic and/or basement. Relatively easy repair. Find a local hvac supply dealer that carries your brand of furnace. Tell him the model and serial number, and he can give you a direct replacement and tips to install. Takes 2 min. Good luck.|||On most units:


1. On the blower panel there should be round plastic glass, you should be able to peer through and see the LED flashing if the LED is off it could mean that there is no power.


2. Count the flashes.


3. Remove the blower panel and on the inside of the panel you should find a sticker with the fault codes.


4. This will tell you what%26#039;s happening in most cases if it%26#039;s furnace related, It will not tell you how to repair it but sometimes will let you know if it%26#039;s a circuit board problem.