Bosch
No Cool Call from Thermostat
Thermostat does not call for cooling even when room is warm and setpoint is lower than room temperature.
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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
Cooling mode disabled in settings, Y (compressor) wire not connected or broken, Thermostat configured as heat‑only, Faulty cooling relay output on thermostat
How to Fix / Troubleshooting
Safety: Turn off power to the air handler/heat pump before changing wiring.
- Check mode: Ensure the thermostat is in COOL or AUTO mode and the cooling setpoint is below room temperature.
- Verify Y wiring: Confirm the Y (or Y1) wire is connected at both the thermostat and the Bosch outdoor unit/air handler control board.
- Installer configuration: In the advanced menu, verify that cooling is enabled and that the system type (heat pump vs. straight cool) is correct.
- Bypass test: At the control board, jumper R to Y (and G if needed). If the outdoor unit and blower start, the thermostat or its wiring is suspect.
- Replace thermostat if necessary: If equipment responds to a jumper but not to the thermostat, the cooling output relay may be defective.
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Repair Difficulty
Medium
3/5
Required Part
Bosch Smart Thermostat Main Control Assembly
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