B0104Sensor Cleaning Air Blower Actuator A Control Relay
- Generic OBD-II code · Body
- Can trigger limp mode
- How the car detects it
- B0104 points at the relay that switches power to blower A. A fan motor draws more current than a module output can carry, so a relay is a natural choice: the module energises the coil (terminals 85/86 in HELLA's scheme) and the contact (30/87) feeds the motor. HELLA's relay brochure explains that coils may carry a diode or resistor against switch-off spikes and that relays are checked for coil resistance and contact voltage drop. Faults here are an open or shorted coil, welded or burnt contacts, or a missing feed. Ford's US12115948B2 places the blower on the sensor bracket, and the Ford tiara uses that air to shield lenses from insects, as eeNews reports. No carmaker publishes B0104; the B-side relay is B0105.
- What you may notice
- Blower A dead, or running without command if contacts are welded
- No relay click when cleaning is requested
- Sensor cleaning warning with possible loss of assistance functions
- Likely causes
- LikelyBurnt or welded contacts in the blower A relay
- PossibleRelay coil open or its control wire interrupted
- PossibleBlown fuse or loose socket on the relay supply side
- Repair
- Easy · Often possible to do yourself.Typical cost: €20 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.