E19
Bosch
System Configuration Mismatch
Thermostat displays E19 and indicates an incompatible HVAC system configuration detected.
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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
Thermostat configured for heat pump but connected to conventional system, Incorrect number of stages set in installer menu, Miswired O/B reversing valve or auxiliary heat, Unsupported multi‑zone or proprietary Bosch control bus configuration
How to Fix / Troubleshooting
Safety: Turn off power to the HVAC system at the breaker before changing wiring.
- Identify system type: Confirm whether your system is a heat pump, conventional furnace/AC, or boiler with zone valves. Check the Bosch thermostat manual for supported configurations.
- Verify wiring: Compare your thermostat wiring (R, C, W, Y, G, O/B, AUX, etc.) to the Bosch installation guide for your system type. Correct any miswired terminals.
- Installer setup: Enter the installer/advanced menu and set the correct system type (heat pump vs. conventional), number of stages, and reversing valve operation (O or B).
- Single vs. multi‑zone: If you have a Bosch multi‑zone controller, ensure the thermostat is connected to the correct zone interface and configured accordingly.
- Consult professional: Complex Bosch boiler or multi‑zone systems may require a Bosch‑trained technician to configure properly.
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Repair Difficulty
Hard
4/5
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