Auxiliary blower relay stuck closed or internally faulty; Relay drive wire chafed and shorted to a live supply feed; Corroded or water-damaged connector or fuse box terminals causing cross-connection; Faulty climate control or body control module output driver; Previous wiring repair or aftermarket accessory wired incorrectly into the circuit; Faulty auxiliary blower motor or resistor/control unit pulling the circuit incorrectly.

B2559

Aux A/C Blower Motor Relay Circuit Short to Battery.

Other
Body
Manufacturer code
Medium severity

How this code is built

B: SystemBody
2: Defined byThe manufacturer
5: AreaBody area 5
59: FaultThe specific fault in that area

What it means

B2559 is a body code meaning the control unit has detected a short to battery voltage in the circuit for the auxiliary A/C blower motor relay. The module monitors the relay drive circuit and sets the code when it sees voltage on the line when it is commanding it off, or when the feedback does not match the command. The exact circuit layout and which module controls the relay depend on the make and model, so this guide is general.

Symptoms

Auxiliary (rear) blower fan runs constantly or will not switch off
Auxiliary blower does not respond to the controls
Rear air conditioning or heating not working correctly
Climate control warning or fault message on some models
Relay clicking, hot, or draining the battery after the car is switched off

Possible causes

Auxiliary blower relay stuck closed or internally faultylikely
Relay drive wire chafed and shorted to a live supply feedlikely
Corroded or water-damaged connector or fuse box terminals causing cross-connectionpossible
Faulty climate control or body control module output driverpossible
Previous wiring repair or aftermarket accessory wired incorrectly into the circuitpossible
Faulty auxiliary blower motor or resistor/control unit pulling the circuit incorrectlyrare

How to diagnose

Read all stored codes and freeze frame data, noting whether other climate or body codes are present, then check whether B2559 returns after clearing
Use the wiring diagram for the specific model to identify the auxiliary blower relay, its fuse and the controlling module
Inspect the relay, fuse box and connectors for moisture, corrosion, heat damage or signs of previous repairs
Check for accessories or non-standard wiring tapped into the blower circuit
Swap the relay with a known good identical one, or test it on the bench for coil and contact operation
With the relay removed and the ignition on, check the drive circuit for unwanted voltage at the relay socket and at the module connector
Inspect the harness along its route for chafing, particularly at grommets, door or seat transitions and sharp edges, then test for continuity and short to supply
If wiring and relay test good, check the module output and power supplies per the manufacturer's procedure before condemning the module

How to fix

Replace a faulty or stuck relay with the correct specification part
Repair or replace the shorted wiring and secure it clear of sharp edges
Clean or replace corroded connectors and terminals and cure any water ingress
Correct or remove faulty non-standard wiring added to the circuit
Replace the faulty control module only after the circuit is proven good, with any programming the manufacturer requires

Can I keep driving?

Medium severity

The car can usually be driven, but a relay stuck on can flatten the battery or overheat the circuit, so get it checked soon. If you smell burning or the blower cannot be switched off, disconnect or remove the relay or fuse for that circuit until repaired.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.