my ecobee says it's cooling but no cold air is coming out, the fan is just running, help?

Diagnosis

This issue is typically caused by a breakdown in communication between the ecobee SmartThermostat Enhanced and the outdoor condensing unit. When the thermostat display says "Cooling," it means the device has closed the R-to-Y circuit, sending 24VAC to your HVAC system. However, if only the indoor blower fan is running, the outdoor compressor is not engaging. This is often due to a tripped outdoor disconnect switch, a failed dual-run capacitor in the condenser, or a "short cycle" protection lockout triggered by the system. To confirm the root cause, check the outdoor unit. If the fan on the condenser is spinning but the compressor isn't humming, the capacitor is likely dead. If the outdoor unit is completely silent and lifeless while the indoor fan blows warm air, the issue is likely a power failure at the condenser or a blown 3-amp or 5-amp fuse on the furnace/air handler control board. If you recently changed settings, you may have accidentally set the "Fan Control" to "Always On" or "Circulate," which makes it look like the system is cooling when it is actually just moving air.

How to Fix It

Follow these steps to isolate and resolve the cooling failure:

1. Verify Thermostat Wiring: Pull the ecobee unit off the wall plate. Ensure the wire connected to the **Y1 terminal** is secure and not frayed. If the wire is loose, the signal to cool never reaches the outdoor unit.
2. Check the Outdoor Disconnect: Go to the outdoor condensing unit. Locate the metal disconnect box mounted on the wall nearby. Open the cover and ensure the pull-out switch is fully inserted or the circuit breaker is flipped to "ON."
3. Reset the HVAC Control Board: Turn off the breaker for your HVAC system at the main electrical panel. Wait exactly 60 seconds. Flip the breaker back on. This clears "lockout" codes on the control board that may be preventing the Y1 signal from engaging the compressor.
4. Test the "Cool" Threshold: On the ecobee screen, go to Main Menu > Settings > Comfort Settings. Lower the set temperature to 5 degrees below the current room temperature to force a "Call for Cool." Listen for a distinct "click" from the indoor air handler.
5. Inspect the Air Filter: If the filter is clogged, the evaporator coil can freeze, causing the system to shut down the compressor while keeping the fan running to thaw the ice. Replace any filter with a MERV 8 or MERV 11 rated filter.

If That Didn't Work

• Test the Capacitor: If the outdoor unit is humming but not starting, the dual-run capacitor (the cylindrical silver part) has likely failed. You can identify this by looking for a "bulged" or leaking top on the capacitor. This requires a multimeter to test for microfarads (µF) and replacement with an exact match (e.g., 45/5 µF).
• Bypass the Thermostat: To determine if the ecobee is the problem, turn off the power and jump the R wire to the Y1 wire on the wall plate using a small piece of insulated copper wire. Turn the power back on. If the AC starts immediately, the ecobee unit or its internal relay is faulty.
• Check the Float Switch: Look at your indoor evaporator coil drain pan. If the primary condensate drain is clogged, the float switch (a small plastic device on the PVC pipe) will trip and cut power specifically to the Y1 (cooling) line to prevent a flood, while allowing the fan to continue running. Vacuum out the drain line from the outside.
• Inspect the Fuse: Open the indoor air handler panel and locate the control board. Look for a small automotive-style blade fuse (usually 3A or 5A). If the filament is broken, the thermostat cannot send power to the outdoor unit. Replace it with an identical amperage fuse.

Heads Up

• Avoid "Rapid Cycling: Never rapidly change the temperature up and down to "test" the AC. This can trigger the compressor's internal thermal overload protection, which may take 2-4 hours to reset.
• Check Voltage: If you are using a C-wire, ensure it is providing a steady 24VAC. Low voltage can cause the ecobee to trigger a cooling call that isn't strong enough to engage the contactor outdoors.
• Seasonal Maintenance: Use a garden hose to gently clean the outdoor condenser coils every spring. Dirt and cottonwood buildup increase head pressure, which can cause the compressor to trip its internal breaker.