E07
Johnson Controls
Cooling Output Relay Failure
E07 displayed and thermostat will not energize cooling outputs; AC does not start even though cooling is requested.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed Y/Y1 relay on thermostat PCB, Burned relay contacts, Miswired Y/Y1/Y2 terminals, Shorted compressor contactor coil circuit
How to Fix / Troubleshooting
Safety: Turn off power to the air handler/furnace and outdoor condensing unit at the breakers before working on wiring.
- Step 1 – Verify wiring: Remove the thermostat and confirm that Y/Y1 (and Y2 if used) are correctly wired and not shorted to other terminals.
- Step 2 – Inspect at air handler: At the indoor unit control board, inspect the thermostat cable and Y circuit for damage or shorts.
- Step 3 – Voltage test: Restore power. With a call for cooling, measure between R and Y/Y1 at the thermostat. If no 24 VAC is present while E07 is displayed, the thermostat relay is likely failed.
- Step 4 – Bypass test (advanced): With power off, temporarily jumper R to Y at the air handler control board. Restore power briefly to see if the outdoor unit starts. Remove jumper immediately after test.
- Step 5 – Replace thermostat: If the system runs with a jumper but not with the thermostat, replace the thermostat main control board or entire thermostat.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board (Cool Relay)
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