If Your Thermostat Stops Working, This is What it Might Mean

Here are some tips to try to get the right temperature

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Introduction

Try these simple fixes before replacing your thermostat.

Tools Required

  • Needle-nose pliers

Are you finding that your house has to get really cold before the furnace kicks in, even with the thermostat set at an otherwise normal temperature? Don’t panic, not yet.

You might not need to install a new thermostat; it might just need to make some adjustments to the one you’ve already got. If this is happening to you, we recommend following three simple steps to adjust it: (1) adjust the thermometer; (2) level the thermostat; and (3) adjust the anticipator.

Before you start making these adjustments, the first thing to do is to remove the thermostat from the wall. On the backside of the thermostat, directly behind the mercury switch and coil on the front, you’ll find a small metal nib (some models have a slot for a screwdriver). Using a regular thermometer as a guide, adjust the thermostat’s thermometer. If you have a rectangular model, make sure it’s level when you replace it on the wall.

What’s the anticipator on a thermostat and what does it do?

The anticipator controls the length of the on/off cycles of your furnace. For maximum comfort and efficiency, the anticipator should keep the temperature of the room from varying more than two or three degrees.

To adjust it, remove the thermostat cover and look for a scale with the word “longer” on it and an arrow. If your furnace doesn’t come on unless the room is really cold, you’ll need to make the cycles shorter so the furnace will come on sooner. To do this, move the anticipator, in small increments, in the opposite direction of the arrow.

Required tools for this project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

You’ll need a pair of needle nose pliers, a flat-blade screwdriver and a torpedo level.

Project step-by-step (2)

Step 1

Adjusting the thermometer

On the backside of the thermostat, directly behind the mercury switch and coil on the front, you’ll find a small metal nib (some models have a slot for a screwdriver). Use this to adjust the thermostat’s thermometer, using a regular thermometer as a guide.

Fixing thermostat adjustment image if your thermostat stops workingTMB Studio

Step 2

Level the thermostat and adjust the anticipator

Be sure the thermostat itself is level. To adjust the anticipator, remove the thermostat cover and look for a scale with the word “longer” on it and an arrow. Move the anticipator in small increments. Before you make any further adjustments, it’s important to test each one you make. With that, your home heating system should begin working with the thermostat the proper way.

Adjusting mounting slot, anticipator, mercury switch on image of thermostatTMB Studio