Bosch Mini Split F4 Error Code

What F4 means

F4 means an outdoor unit EEPROM parameter error on Bosch Climate 5000 Gen 2 systems - the outdoor (or indoor) main chip is not getting a valid response from the memory chip that stores unit settings. The service manual groups it with E0 (indoor equivalent): causes are incorrect installation of the indoor-to-outdoor control wiring or a faulty PCB. A brief power disturbance can also cause a one-time memory fault.

First checks before service

This page currently documents the safe reset triage. If the code returns, use the linked source manual or a qualified technician for code-specific diagnosis.

1. 1. One-time fault event (power disturbance or transient sensor reading) common DIY

   Check: Power-cycle at the breaker/disconnect (or unplug for CPAP), restore, and run the system while watching for the code.

   Fix: If the code does not return after a full run cycle, the fault was transient — monitor, no repair needed.

2. 2. Fault persists after a clean reset occasional pro only

   Check: If the code returns immediately or every session, note the conditions (startup, heating, after rain).

   Fix: A persisting code points at the component the manual assigns to this code — that repair is technician territory.