Why Is My Thermostat Blinking with Cool On?

Your thermostat is the brains behind your HVAC system – telling the air conditioner or heat pump when to start cooling or telling the furnace or heat pump system when to warm things up. It also knows when to shut things down or delay startup. That’s why occasionally, you may see Cool On flashing on a thermostat. You may also see Starting Soon.

If this happens to you, don’t panic. In most situations, a thermostat showing Cool On and flashing simply indicates the thermostat is delaying startup for one of two reasons.

Some programmable and smart thermostats have a built-in safety feature that protects the compressor. If the compressor just shut off, the thermostat may delay an immediate re-starting to avoid overheating or short cycling.

After an appropriate amount of time, the thermostat will signal the compressor to start up again.

The other instance where you might see Cool On blinking on a thermostat is after a power loss. A power outage can cause a power surge, which can harm your compressor. As a safety measure, the thermostat institutes a startup delay, allowing the compressor to reset and start up again safely.

Keep in mind that different brands of thermostats will have different indicators. For instance, while it’s set to Cool, the thermostat may display Wait if it is delaying startup. Refer to your owner’s manual for more information and consult with an HVAC professional if your thermostat or HVAC system is not working as it should.

To keep your HVAC system operating at peak performance, you need to keep up with regular HVAC maintenance. This includes DIY tasks and scheduling biannual visits from an HVAC company.

DIY maintenance includes cleaning or changing out your air filters. Refer to our HVAC air filter cleaning and maintenance guide for some tips. You can also make sure that the outdoor unit is clear from debris or encroaching shrubbery, vines, or other plant material. Make sure that indoor return air vents and registers are clear and not blocked by drapes or furniture.

You should also schedule professional HVAC maintenance each spring and fall. During these visits, the HVAC technician will clean and test your HVAC system, including your thermostat. These regular visits allow the HVAC technician to detect and fix small problems before they become big ones.

If your thermostat stopped working or is acting up and you can’t figure out why, call your local Trane dealer for assistance. If it’s a Trane smart thermostat and you have granted Trane Diagnostics remote access, they may be able to troubleshoot the issue and fix it remotely.

If you need a new thermostat or have other HVAC issues, they can also schedule an on-site visit to get your heating and cooling system working again.

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Michael Morey, Smart Thermostat Product Manager

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