t9 says "equipment running" but my furnace or ac isn't actually on, it's just blowing room temp air.

Diagnosis

The "Equipment Running" message on a Honeywell Home T9 indicates that the thermostat's internal relays have closed and it is sending a 24VAC signal down the control wires to your HVAC system. When you feel room-temperature air, it means the blower motor (fan) is active, but the actual heating element (gas valve/electric strips) or the cooling component (compressor/condenser) has failed to engage. This creates a "phantom run" where the thermostat thinks the job is being done, but the equipment is stalled. This discrepancy usually stems from one of three root causes: a tripped float switch in the condensate pan (which cuts power to the condenser but allows the fan to run), a blown 3-amp or 5-amp fuse on the furnace control board, or a loose connection at the R, W, or Y terminals. To confirm, you need to determine if the signal is leaving the T9 and if the equipment is receiving it. If the fan is blowing, the G-wire is functioning, but the specific call for heat (W) or cool (Y) is being interrupted between the wall plate and the appliance.

How to Fix It

To isolate whether the issue is the T9 hardware or your HVAC system, follow these precise steps to trigger a forced hardware test:

1. Remove the T9 faceplate from the wall bracket to ensure the pins are seated correctly. Snap it back into place firmly.
2. On the thermostat screen, tap Menu > Settings > Advanced Settings.
3. Select Installer Setup. When prompted for the code, enter 4114.
4. Navigate to Test Equipment.
5. Select Cool (or Heat, depending on the failing mode). This bypasses the temperature sensors and forces the Y (Cool) or W (Heat) relay to close.
6. While the test is running, go to your outdoor condenser unit. Listen for the "click" of the contactor. If the fan is spinning but the compressor isn't humming, the issue is a failed capacitor or a tripped high-pressure switch.
7. If the outdoor unit is completely silent, go to your indoor furnace/air handler. Locate the control board and check the automotive-style blade fuse (usually a purple 3A or amber 5A fuse). If the filament is broken, replace it with an identical amp rating.
8. Check the condensate drain line. If the secondary pan has water in it, the float switch has broken the 24V circuit to the Y-wire to prevent flooding, which is why the T9 says "Running" but the AC stays off.

If That Didn't Work

• Perform a Jumper Test: Turn off the breaker to your HVAC. Remove the T9 from the wall. Using a small piece of insulated copper wire, jump the R (Red) terminal directly to the Y (Yellow) terminal for cooling or W (White) for heating. Turn the power back on. If the system kicks on immediately, the T9's internal relay is faulty or the C-wire is providing insufficient voltage.
• Verify Common Wire (C-Wire) Stability: The T9 requires a constant 24VAC. If you are using a "C-wire adapter" or a power-stealing setup, the thermostat may have enough power to display "Equipment Running" but not enough to maintain the magnetic hold on the relay. Install a dedicated 24V transformer if the C-wire is unstable.
• Check the Air Filter and Limit Switch: If this is happening during a Heat call, your furnace may have tripped the "High Limit Switch" due to a clogged filter. The furnace shuts down the burners for safety but keeps the blower running to cool the heat exchanger. Replace your 16x25x1 filter and reset the furnace power.
• Inspect the Contactors: For AC issues, the outdoor contactor may be "pitted" or burnt. Even if the T9 sends the signal, the contactor may fail to pull in. Use a multimeter to check for 24VAC at the contactor coils; if voltage is present but the unit isn't starting, the contactor is dead.

Heads Up

• Never replace a 3-amp fuse with a 5-amp fuse; doing so can permanently fry the integrated circuit board of your furnace, leading to a $400+ replacement.
• Avoid using "bridge" wires or twisting multiple wires into one T9 terminal; the T9 uses push-terminals that require a clean, stripped end to ensure a solid 24V connection.
• If you have a heat pump, ensure the "O/B" reversing valve setting in the Installer Setup is correct; if inverted, your AC will blow hot air and your Heat will blow cold air.
• Clear your condensate drain line with a wet/dry vacuum every six months to prevent the float switch from triggering a system shutdown.