My Honeywell thermostat screen will not change when I press the buttons but the temp does change

SOURCE: honeywell round mercury thermostat - heat not coming on

If you tip the mercury switch so that it makes contact and the furnace doesn't start, it isn't the t-stat. Check the connections, then start checking the furnace.
In any case, ditch the mercury t-stat (recycle it properly) and get a new programmable one if at all posible. It will pay for itself many times over by turning your heat down in the middle of the night and back up by morning.

SOURCE: honeywell thermostat

If you lost the manua, you can go to their site and download it.

Hard to help more without a model number. Sorry.

Geno

SOURCE: Thermostat unit not cooling house.

Okay. Here's what I suspect in order of probability:

- low refrigerant charge
- contactor not getting 24 volts from controller (controller problem)
- bad contactor
- bad capcitor

I'd start with the charge, as suggested by mastatech. But if it is low, you'll need a service call, anyway, so pressing the needle valve may not be necessary.

I'm assuming you're not going to be taking the unit apart and testing stuff, so you'd need a service call for that as well.

I guess bottom line is, call for service. At least, I think we've ruled out simple stuff which will avoid paying for a service tech to come out and flip a switch.

Maybe mastatech has some other recommendations.

SOURCE: Honeywell thermostat won't regulate temp properly

Is there a setting on your thermostat that makes the unit stay on for 10, 15, 20, 25 minutes after you reach set temp. You can change this setting by looking at your manual for the thermostat. Not sure if there is one for this thermostat but mine has one. Mine was running 15 min after set temp and making it cool down 2 degrees lower than set temp. Hope this helps.

SOURCE: The thermostat worked correctly for months then

Go to honeywell.com
Under red welcome sign
Bottom red highlighted box literature/image search
Type in thermostat model number
Click on arrow to right
Then click on the PDF files owners manual / installation instructions
If you can’t find what you want, the bottom left and bottom of web
Page, they have homeowners assistance and Home products to get the help you need