Vol.2, No.8

Do it yourself: troubleshooting common thermostat problems

Homeowners can resolve many common thermostat problems. Here are a few suggestions for troubleshooting in both new homes and older houses.

A broken thermostat
You may notice that your home is suddenly too hot or too cold. Perhaps the fan runs constantly, but the temperature gauge does not register a change. This could be a sign of aging equipment or could simply be the fault of the thermostat.

If your heating and air conditioning unit is more than fifteen years old, you may certainly be looking at replacement. First, though you should look at the options.

Before troubleshooting your thermostat, check to see if all filters are clean and all hoses to and from the units themselves are free of wear.

If these are not causing problems, then it is time to look at specific issues and possible solutions. Your thermostat could have aging wiring that is faulty or the transformer may require replacing.

Always check the owner's manual for the system first, if it is available.

For a wireless system, make sure you are using the correct batteries: AA Lithium. If the system is running at inconsistent times, then you may have inadvertently installed alkaline batteries. Regular batteries will run out of juice quickly in a wireless system, especially if the backlight is on or used frequently to check the readings.

Does the heater or air conditioning fail to come on when the home's temperature is too cold or too warm? Or does it trigger on when there is no need? There are several different reasons for this to occur.

First, study the location of the thermostat. Is it in a drafty hallway? Is it too near a heat source? If no outside sources are to blame, you will need to check behind the thermostat and in the wall itself.

Thermostats run on very low voltage, but it is always a good idea to turn off power, both to the unit and to the thermostat. Remove the thermostat cover by either prying off or removing the screws, depending on the model. When the cover is off, can you detect any unusually cool or warm air coming through from the wall space? If so, remove the entire unit and caulk or add extra insulation around the opening.

If you have a regular, house-type thermometer that you know to be accurate, hang it next to the thermostat. Check the readouts every hour or so for a comparison. This will help you to determine its operation, both before and after trying simple repairs and cleaning.

A thermostat may need cleaning to eliminate erratic operation. Accumulated dust is a common culprit.

Depending on the model, here are some areas to check. First, you should have a small paintbrush, a screwdriver, and a voltmeter.

The anticipator is a small metal tab positioned in front of an arcing printed scale. Give it a light push in both directions. This easy step may solve the problem.

Give the thermostat's interior a light dusting with a small, soft paintbrush. Be sure to clean the contacts, which are small metal plates within the unit. The wires coming from the transformer attach to the contacts. Do not touch any of the interior parts with fingers.

If the base is loose, retighten the screws. Check the wires coming from the transformer. If any corrosion is present, remove the wire from the contact and clean. Use a wire stripper to remove the surrounding insulation, cut back the wire, and reconnect.

Make sure the terminal screws are tight.

A thermostat's terminals are marked with "Y," which is usually a blue wire, "W" is a white wire, "G" is typically black, and "R" is red. You can use a short piece of wiring with the ends stripped away to create a "jump" between connections. The electricity will need to be on for this test. Place one end of the jump wire on the Y and the other end on the G - if the fan comes on during this connection, your thermostat could be faulty.

You may need to test the transformer if nothing seems wrong with the thermostat. You can use a voltmeter or a multitester. If you are using a multitester, set the dial to ACV 50 and connect a probe to each of the terminals. This step will allow you to test for current. If there is none, one final step should be to check power coming in to the transformer. Use the multitester or voltmeter to probe the hot wires and the neutral wires and tighten the contacts if necessary.

If the problem is with an older thermostat, and the system is not on a heat pump, you should consider replacing the thermostat with a digital model. It will increase the efficiency of your unit and many styles are available that can be programmed to suit your daily schedule.

If you are not comfortable working on the inside of your thermostat, do not hesitate to call a professional. Certainly, if these suggestions do not seem to help, then it is time to place that call.

Even if your system seems to be having problems not listed here, try the troubleshooting tips first. You may be able to solve the problem and avoid the expense of calling an outside professional.