why does my new sensi touch 2 make a faint clicking sound every few minutes? the old one didn't do that.

Diagnosis

The faint clicking sound you are hearing from your White Rodgers Sensi Touch 2 is the physical actuation of the internal electromagnetic relays. Unlike older, non-smart thermostats that often used silent electronic switches or heavily dampened mechanical contacts, the Sensi Touch 2 utilizes a series of small relays to bridge the 24VAC power from your transformer to the specific control wires (Y, W, or G) leading to your HVAC equipment. This clicking occurs every time the thermostat's logic board decides to initiate or terminate a "call" for heating, cooling, or fan operation. If you hear it every few minutes, it typically indicates "short-cycling," where the system is rapidly turning on and off to maintain a very precise temperature set point. This is especially common if the thermostat is installed in a drafty area or near a heat source, causing the internal thermistor to fluctuate rapidly. You can confirm this is the cause by observing the screen during the click; you will likely see the "Cooling" or "Heating" status toggle on or off at the exact moment of the sound.

How to Fix It

Since this is a mechanical function of the hardware, you cannot "disable" the relay, but you can eliminate the frequency of the clicking by adjusting the temperature swing (differential) and placement settings to prevent short-cycling.

1. Access the main menu on the Sensi Touch 2 home screen by tapping the gear icon or the menu button.
2. Navigate to Settings and then select Advanced Settings.
3. Locate the Temperature Swing or Differential setting. If it is set to a very tight tolerance (e.g., 0.5°F), increase it to 1.0°F or 2.0°F. This forces the system to wait for a larger temperature change before triggering the relay, reducing the number of clicks per hour.
4. Check your Fan Control settings. If the fan is set to "On" rather than "Auto," the relay for the G-wire remains closed, but the Y or W relays will still click. Switching to "Auto" ensures the fan only runs when active cooling or heating is required.
5. Verify the Cycle Rate settings if available for your specific HVAC equipment type (Electric vs. Gas). Ensure the "Minimum Off Time" is set to at least 5 minutes to protect your compressor and reduce relay chatter.

If That Didn't Work

• Relocate the Thermostat: If the unit is mounted on an exterior wall or directly above a supply vent, the "ghost" temperature swings will cause the relay to click constantly. Moving the unit to an interior wall or installing a wall shield/gasket behind the backplate to block holes where cold air from the wall cavity leaks in can stop the erratic clicking.
• Check C-Wire Stability: If the clicking is accompanied by a screen flicker or a reboot, you may have a loose Common (C) wire connection. A fluctuating power supply can cause the relays to trip and reset. Tighten the screw terminals on the backplate and ensure the wire is stripped exactly 1/4 inch.
• Inspect the HVAC Air Filter: A clogged filter can cause the system to overheat and trip a high-limit switch. This shuts down the HVAC unit, causing the Sensi Touch 2 to lose the "load" and reset the relay, then try again a few minutes later. Replace your 16x25x1 or 20x20x1 filter to ensure steady airflow.
• Test for Voltage Spikes: Use a multimeter to check the voltage between R and C. It should be a steady 24-28VAC. If you see significant drops when the relay clicks, your transformer may be undersized for the smart load, causing the relay to "chatter."

Heads Up

• Normal Operation: Remember that a single click every 15-30 minutes is a sign of a healthy, functioning system; it confirms the physical connection is being made to your furnace or AC.
• Avoid Tight Tolerances: Setting your temperature swing too low (under 1 degree) can lead to premature wear of the relay contacts and put excessive strain on your HVAC compressor.
• Wall Insulation: Always use the provided wall anchors and consider using a bit of plumbers putty or silicone in the wire hole behind the thermostat to prevent "wall drafts" from tricking the sensor.
• Firmware Updates: Ensure your Sensi Touch 2 is connected to Wi-Fi; the device automatically downloads firmware updates that can optimize the cycling logic to reduce unnecessary relay activations.