Cohortskates

Thermostats play a big role in heating and cooling efficiency. They suffer most from getting dirty. Wires do come off of terminals. Sometimes a thermostat needs replacing. A thermostat is a sensitive item of equipment. Some have maintenance warnings. Pay attention.
Don’t tamper with calibration. But you can become familiar with the thermostat’s workings. Remove the cover and look at the mechanism. You’ll find some with coil springs for calibration; others have transistors. Some models have terminals on the front panel only; others have them on front and back.
Dirt and lint—even hair—in the mechanism brings on thermostat malfunction. Clean the coil-type with a thin piece of paper. Work in and around the coil gently, to avoid bending it out of calibration. With your breath only (no compressed air), lightly blow dust from non- spring types. Do not use a vacuum cleaner or a blowing appliance such as a hair dryer.
Loose wires prevent a thermostat from working properly. Turn off the circuit (at the breaker) that powers the furnace and the thermostat. Remove the cover, Inspect the screw terminals that hold wires. Even if they appear tight, tug on the wires gently with your fingers or push with your screwdriver. Tighten any loose wires. Watch out for loose copper strands that may touch something they shouldn’t. Stranded wires must be twisted tight before being fastened under the terminal screws.
Remove the thermostat from the wall and look for loose wires behind it. Do this gently. You don’t want to fish loose wires out of the wall. If cleaning and tightening do not remedy an ailing thermostat, you need a furnace technician.