Thermostat calls for heat but furnace starts and stops frequently, with very short run times

Safety: Low-voltage thermostat work can usually be done with power off at the furnace.

• Thermostat settings: For digital thermostats, set the cycles-per-hour or swing setting according to Bosch recommendations (often 3–5 cycles per hour for furnaces).
• Location: Relocate the thermostat away from drafts, direct sunlight, or supply registers.
• Room sensor: If using a Bosch room controller with remote sensor, ensure the sensor is properly connected and not influenced by local heat sources.