Thermostat clicks but the system does not start
A click from the thermostat usually means it has sent the call for heating or cooling. Sensi says you should hear a soft click within a few seconds of changing the setpoint. The thermostat cannot tell whether the equipment answered, so if nothing starts after 5 minutes, the problem is past the thermostat and needs a licensed HVAC technician.
What is the click you hear?
The click is the thermostat switching on its call to your heating or cooling. Sensi spells this out in its troubleshooting pages, and it is the clearest description any manufacturer we checked gives. Raise the setpoint a few degrees above the room temperature, or lower it below for cooling, and within a few seconds the thermostat should make a soft clicking sound. On a Sensi Smart, the word "Heating" or "Cooling" appears near the set temperature at the same time. On a Sensi Touch or Touch 2, the screen turns orange for heat or blue for cooling, and Sensi says you will still hear the click.
So a click is good news about the thermostat. It means it has decided the room needs heating or cooling and has sent that request on.
Why would it click and nothing start?
Because the click is the request, not the answer. Sensi says plainly on its loss of cooling page that the thermostat does not know whether the cooling system is on or not. It tries to start the system and has no way to confirm the result. If something past the thermostat is not responding, the thermostat will go on showing "Cooling" or "Heating" as if all is well.
There are also normal reasons for a short gap between the click and air from the vents:
- The equipment takes a moment. Sensi says some heating systems, such as boilers, can take a few minutes to start up after the call.
- A compressor timer is running. Air conditioners and heat pumps are often held off for a few minutes after their last cycle. That is compressor protection. On a Honeywell Home FocusPRO S200, "WAITING FOR EQUIPMENT" under the temperature means this delay is running.
- Only the fan is on. With the fan set to "On", air moves whether or not the heating or cooling runs, which can hide whether anything else started. See fan "On" vs "Auto" and fan circulate mode.
How long should you wait after the click?
About 5 minutes. Honeywell's T4 Pro guide lists "Wait 5 minutes for the system to respond" for a heating or cooling system that does not respond, and the FocusPRO S200 manual says to wait 5 minutes to see if the thermostat makes a heat or cool call. Make one change, then leave it alone for that time.
What can you check on the thermostat?
These are the checks that stay on the thermostat itself:
| Thermostat | Sign it is calling | Thermostat check the maker gives |
|---|---|---|
| Sensi Smart | Soft click and "Heating" or "Cooling" near the set temperature | If there is no click, reset the thermostat and try again. Replace low batteries |
| Sensi Touch and Touch 2 | Click; screen turns orange (heat) or blue (cooling) | If there is no click, reset the thermostat and try again |
| Honeywell Home T4 Pro | Not stated | Mode set to Heat with the setpoint above the room, or Cool with it below; wait 5 minutes |
| Honeywell Home FocusPRO S200 | "HEAT ON" or "COOL ON" in the lower right | If "WAITING FOR EQUIPMENT" shows, wait 5 minutes |
Batteries matter even when the screen looks fine. Sensi says that on the Sensi Lite and Sensi Smart, low batteries may leave the thermostat unable to turn on your system. If yours shows a battery warning, see thermostat low battery message.
Also confirm the mode. A thermostat in Off mode will not call for anything, and a heat setpoint below the room temperature will not either.
When is it no longer a thermostat problem?
When the thermostat clicks, shows that it is calling, the 5 minutes have passed and still no heated or cooled air arrives. Sensi's simple test is to hold your hand over a vent: cold air means the cooling is running, and no cold air means the system may not be starting when the thermostat asks. At that point Sensi's own advice is to contact an HVAC professional to troubleshoot your equipment.
Do not go further than the thermostat. Everything after the click, from the wiring to the equipment, is work for a licensed HVAC technician. The pages for heat on but nothing happens and "Cool On" but the AC is not running cover the screen messages in more detail.
What should you do now?
Is the mode Heat or Cool, with the setpoint on the right side of the room temperature?
- Yes
Has it been at least 5 minutes since the click?
- Yes
Does the thermostat use batteries, and is a low battery warning showing?
- Yes
Replace the batteries, make one setpoint change, and wait 5 minutes again.
- No
The thermostat has done its part. Check the signs at the bottom of this page and call a licensed HVAC technician.
- Yes
- No
Wait the full 5 minutes. A compressor protection delay or a slow equipment start may still be running.
- Yes
- No
Set the mode and move the setpoint a few degrees past the room temperature, then listen for the click again.
Frequently asked questions
- Is it normal for a thermostat to click?
- Yes. Sensi describes a soft click as what you should hear within a few seconds of asking for heating or cooling, together with "Heating" or "Cooling" on the screen of a Sensi Smart. The click on its own is a sign the thermostat is doing its job.
- My thermostat does not click at all. What does that mean?
- Sensi's advice when you hear no click is to reset the thermostat and try again. Also check that the mode and setpoint really ask for heating or cooling, and that the batteries are not low on models that use them.
- Can the thermostat tell me whether the heating or cooling actually started?
- Not directly. Sensi says on its loss of cooling page that the thermostat does not know whether the cooling system is on or not. It sends the request and reports that it did, which is why a click with no result points past the thermostat.
- Should I keep switching the thermostat off and on to make it start?
- No. Make one change and give it the full 5 minutes Honeywell suggests. A compressor protection delay may already be running, and starting over only makes it harder to tell whether the system responded.