What to do if the fan on my Bosch SM048 isn't working?
- DDale GardnerSep 4, 2025
If your Bosch Heat Pump's ECM constant airflow motor isn't operating, there could be several reasons. First, check for 24 VAC between "G" and "C" and verify all wiring connections, as there may be no fan operation signal. Loose wiring can also cause this issue, so check all wiring connections at the motor and control box, ensuring that power and control harnesses are securely connected. Interface board problems could also be the cause; make sure the interface board isn't damaged and that all DIP switches are in the proper configuration. Finally, a faulty motor could be the problem; check the supply voltage to the motor and ensure all motor wires are secure.







