If you’re having trouble regulating your HVAC system and you think your thermostat may be the issue, we’ve got a few suggestions for troubleshooting and correcting the problem. Just ask yourself these five questions to troubleshoot the most common faults with thermostats. If all else fails, there are some other steps you can take to troubleshoot your furnace itself.
1. Is the thermostat on the heat mode and set at the right temperature?
It’s obvious, right? But you may be surprised by how often a “broken” thermostat is simply turned off, set on the cool cycle, or set too low. Start with the obvious things first and you may be back to perfect operation sooner than you think.
2. Have you checked the batteries?
If your thermostat operates on batteries, try a new set and see if that solves the problem. Just as general maintenance, you should check thermostat batteries regularly — especially at the beginning of heating season — and replace every few months to avoid sudden loss of heat. It’s a good idea to keep some spares on hand, too.
3. Is the thermostat calling for heat?
If you’ve checked the batteries and made sure the thermostat is in heat mode, try setting the temperature up a few degrees to see if the furnace kicks in. If not, it may be time to call in the HVAC pros.
4. Does your thermostat have a built-in time delay?
Some thermostats have time delays, as do some furnaces and air conditioning units. If you’ve tried everything else, adjust the temperature setting or turn the system off, then back on, to “reset” it. Wait a few minutes and try again.
5. How old is your thermostat?
Thermostats do wear out. While some can last upwards of 15 years, it’s probably a good idea to think about replacing them after that. Even if your thermostat seems to be working just fine, advances in technology mean you can probably increase the efficiency of your system and lower energy costs by replacing it. And if you’re thinking about getting a new furnace, we recommend you replace your thermostat at the same time. It may save a few bucks to keep the old one, but that minor savings can be readily made up by the long-term savings of a new, more efficient unit.
The new, digital thermostats are much better than the old style mechanical switches or mercury bulbs. Thermostats that contain mercury (you can usually see the little vial of mercury if you peek in the side or top of the unit) were the best in their day but had a 1½- to 2-degree temperature swing (the difference between the off temp and on temp). New electronic thermostats typically operate with a ¾- to 1½-degree swing — even better when matched to a staged or modulating furnace.
But don’t just throw an old mercury thermostat in the trash! They need to be recycled and there’s a process for that. Check here or contact an HVAC professional to recycle an old mercury thermostat.