Why does my thermostat when I set the temperature to 71 go up to 75 and take all night to get back to 71 it's a brand new unit

clean the whole unit then replace the thermostat

what it sounds like happening is the unit is realizing it is falling behind most thermostat s have a 3 degree deadband if they fall 3 degrees or more at a time after running for so long then it will bring on the emergency heat which is located in your inside unit... when it gets really colds and you see this you need to go outside and look is the outside unit still running and is it freezing up on you...also if running check the larger of two pipes make sure the large pipe is hot to touch...based on the description you have given the thermostat is calling for emergency heat but for some reason is not bringing it on or there is a problem with the emergency heat.... hope this helps out some
repost with any additional questions...

Is this thermostat controlled or by control on unit. If it's thermostat I would check to see how far from set point it is off. 4-5 degrees difference from t-stat and actual temperature is not unusual. Does unit come back on if you turn it up? Sorry I'm not much help but I need more information.Thank you.

Since you didn't provide the brand & model of the thermostat, only generic help can be provided.

Most furnaces that run on oil or gas, make hot water all the time, 24 / 7 - winter, summer and everything between so to speak. They are controlled by an aquastat that may be set for any value between 140 - 180 degrees F. This is called "hot start" - simply because when the thermostat is set to a temperature higher than the room (turning heat ON), the water is already hot in the furnace, and is circulated immediately. If it was a "cold start", you'd have to wait for the water in the furnace to heat up from room temperature. This would substantially increase the amount of time it would take to heat the room.

Generally, the "vacation mode" simply halts the program from running. If your thermostat changes temperatures several times during the day / night, it will simply hold the lowest temperature - or a predetermined temperature built in - or chosen by you. You'll need to consult your manual to determine just how your thermostat handles the vacation mode setting. Post again if you can't find the manual - but tell us what brand and model it is.

I hop ethis helps - good luck!

Many heating thermostats don't allow for setting a temperature below 45 degrees F so freeze ups shouldn't be a problem.

If you still have the instructions for the thermostat, then it will show you how to get into the menu and set the swing on the temps. I would try to explain off the top of my head, but its actually quite a bit off numbers to remember. Hope it helps somehow.

Complicated because I need more info....but in General a Boiler should not be on a Programmable Thermostat as it takes too long to heat etc...do you have Radiators in your house???Or ductwork for heat???It will make a difference...if you put the boiler on a program it may come on anyway as some boilers maintain there own internal temperature regardless of the thermostat.....if you want to run it on a program adjust the temperatures so there is only about a 2 degree swing....70...down to 68....back to 70.....etc...there should also be a switch in the thermostat to set for Boiler...or Electric heat...make sure that switch is on...otherwise its difficult to give you a more conclusive answer

Verify 24 volts at the low voltage transformer inside the air handler. If it is OK, jump out the red/green and yellow thermostat wires. If everything comes on, replace the thermostat.

Uniden EWCI936
To get the outside temperature working again, open the outdoor sensor box carefully loosening the one screw with a screwdriver, insert 3 brand new AA batteries, check phone for outside temperature. If not showing on the phone display, try changing the 'channel' setting, just above the batteries. Be careful not to break the tiny switch. Gently use a smaller flathead screwdriver, if needed. There are 3 settings. Mine worked fine on the first setting. If it is showing on the phone set screens, then, carefully screw the lid back on to the sensor box, and re-insert into the sensor wall holder. I keep mine in a plastic bag on a shelf outside, away from sun, so I can get a true reading day or night. It is always a bit warmer in the sunlight than the true outdoor air temperature. Enjoy

Sounds like the Thermostat or board is wired incorrectly(being new)
have the installer come back and rewire it.

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I have seen this is many digital thermostats. The worst problems usually come from the touchscreen thermostats. I would suggest installing a new thermostat. Make sure that you read the instructions before you even remove the old one.