Ecobee – How to Troubleshoot ecobee Thermostat Power Issues

Category: Thermostats > Installation And Setup

Answer:

If your ecobee thermostat has a black screen or will not power on, follow the steps below to identify and resolve the issue.

If You Just Installed Your ecobee

Confirm Thermostat Wiring

1. Verify the R wire is securely connected.

For ecobee models with Rc and Rh terminals:

• Connect the R wire to Rc.

For models with a single R terminal:

• Connect the R wire to R.

2. Verify the C wire is securely connected to the C terminal.
3. If no C wire is present:

• Use a spare wire connected to C at both ends, or
• Install a Power Extender Kit (PEK).

Good to Know

• Only the ecobee3 can power on using either Rc or Rh.
• Most ecobee models require Rc for power.

Verify Power Extender Kit (PEK) Wiring

For Most ecobee Models

• R from PEK → Rc
• G from PEK → C
• W from PEK → W1
• Y → PEK terminal

For Smart Thermostat Enhanced

• R from PEK → R
• G from PEK → C
• W from PEK → W1
• Y → PEK terminal

For Smart Thermostat Essential

• R from PEK → R
• G from PEK → C
• W from PEK → W1
• Y → G/PEK terminal

Also verify:

• PEK C wire is connected to C on the HVAC control board.

Good to Know

• Smart Thermostat Lite and Smart Thermostat Essential do not include a PEK.
• A PEK must be purchased separately if required.

Check Thermostat Mounting

1. Remove the thermostat.
2. Push excess wiring back into the wall.
3. Reattach the thermostat.
4. Ensure there are no gaps between the thermostat and base.
5. Confirm the thermostat clicks firmly into place.

Check HVAC Power

1. Verify the HVAC breaker is ON.
2. Verify all HVAC access panels are properly closed.
3. Inspect the furnace control board fuse.

Common fuse sizes:

• 3 amp
• 5 amp

4. Replace any blown fuse with the same amperage rating.

Check Voltage

Using a voltmeter:

Measure between:

• Rc (or R)
• C

Expected reading:

• 24–29 VAC

If power is still not restored:

• Contact ecobee Support.
• Have photos of the original thermostat wiring and current ecobee wiring available.

If Your ecobee Was Working Previously

Check Circuit Breakers

1. Inspect the electrical panel.
2. Reset any tripped HVAC breakers.

Check Furnace Fuse

1. Inspect the HVAC control board.
2. Replace any blown 3 amp or 5 amp fuse.

Important

• Always replace a fuse with the same amperage rating.

Power Loss During Heating

Possible Cause: Furnace Overheating

A high-limit switch may shut down the furnace to prevent damage.

Common causes include:

• Dirty furnace filter
• Restricted airflow

Recommended Actions

1. Replace the furnace filter.
2. Allow the furnace to cool.
3. Restart the system.

If overheating continues:

• Consult the furnace manufacturer.
• Contact an HVAC technician.

Power Loss During Cooling

Possible Cause: Condensate Drain Blockage

Air conditioning systems create condensation.

If the drain line becomes blocked:

• Water backs up.
• A float switch or wet switch may shut down power to the HVAC system.

Recommended Actions

1. Inspect the condensate drain line.
2. Remove any blockage.
3. Verify water flows freely.

Consult the HVAC manual for cleaning procedures.

Check Voltage

Using a voltmeter:

Measure between:

• Rc (or R)
• C

Expected reading:

• 24–29 VAC

If voltage is not present:

• Follow manufacturer troubleshooting procedures.
• Contact an HVAC technician if necessary.

Good to Know

• ecobee thermostats do not contain an internal battery or power source.
• The thermostat receives power directly from the HVAC system.
• If HVAC power is interrupted, the ecobee thermostat will shut off.