Bosch Mini Split F4 Error Code

Updated 2026-08-29 · review status: manual-verified Last verified: 2026-08-29

Quick answer

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.

Severity: high · DIY difficulty: intermediate

Safety

Only a power-cycle reset and visual checks you can do without removing any panel. Do not open covers, unplug or test sensors, spray anything into the unit, connect gauges, or replace PCBs - high-voltage inverter components and refrigerant work are technician-only.

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.

Code meaning varies by series

  • Bosch Climate 5000 Gen 2 / legacy: Outdoor unit EEPROM error (ODU service manual: EEPROM parameter error, E0/F4; LED pattern 4 lit on the outdoor lamp group)
  • Gen 3 equivalents: EH 00 / EH 0A (indoor board) or EC 51 (outdoor board)

Causes, ranked

  1. 1. Temporary control-memory fault after a power disturbance occasional diy-ok

    Check: Power off, wait two minutes, restart the unit once.

    Fix: One reset only. If F4 continues, stop resetting and schedule service.

  2. 2. Incorrect installation of the indoor-to-outdoor control (communication) wiring occasional pro-only

    Check: Technician only: verify control wiring routing away from power conductors, correct terminals, and continuity.

    Fix: Technician: correct or replace the control wiring per the installation manual.

  3. 3. Faulty outdoor (or indoor) main PCB / EEPROM chip occasional pro-only

    Check: Technician only: follow Bosch's published procedure - replace indoor main PCB, then outdoor PCB if the error persists.

    Fix: Technician: replace the indoor main PCB; if F4 continues, replace the outdoor PCB.

  4. 4. Incorrect or incompatible replacement board or configuration occasional pro-only

    Check: Technician only: confirm board part number and application matches the model.

    Fix: Technician: install the correct board and redo option configuration.

Related codes

bosch/e0 · bosch/ec51 · bosch/e1

Commonly searched as: "bosch f4" · "bosch error code f4" · "bosch air conditioner f4"

Sources

  • Bosch Climate 5000 Series service manual (manualslib) - 8.1 EEPROM parameter error E0/F4 — verified 2026-08-29
  • Heat Pump Answers - Bosch Mini Split Error Codes (E0/F4 EEPROM parameter error, published procedure) — verified 2026-08-29
  • SplitAtlas Bosch F4 page (outdoor unit EEPROM error) — verified 2026-08-29