Bosch
Unstable Power or Internal Reset
Thermostat reboots randomly or the screen flickers during operation.
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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
Loose R or C connection, Marginal 24 V transformer capacity, Short spikes from contactor coils, Internal power regulator fault on thermostat PCB
How to Fix / Troubleshooting
Safety: Turn off power to the HVAC system before tightening any wiring.
- Check wiring at thermostat: Remove the thermostat and ensure R and C wires are firmly secured with no corrosion or broken strands.
- Inspect at control board: Tighten R and C terminals and verify the thermostat cable is not damaged or pinched.
- Measure voltage under load: With a multimeter, monitor 24 V between R and C while the system starts. Large dips may indicate an undersized or failing transformer.
- Reduce load: If multiple devices share the same 24 V transformer, consider adding a dedicated transformer for accessories.
- Replace thermostat if needed: If power is stable but reboots continue, the thermostat’s internal power circuitry may be defective.
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Repair Difficulty
Medium
3/5
Required Part
Bosch Smart Thermostat Main Control Assembly
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