Aux Blower Sense Switch Circuit Fault
The B2580 code indicates a fault in the auxiliary blower sense switch circuit, which is part of the vehicle's HVAC system. This circuit monitors the position or status of the auxiliary blower switch, typically controlling airflow in the rear or auxiliary cabin area. The HVAC control module detects an abnormal signal, out-of-range reading, or an open circuit in the feedback loop from the auxiliary blower switch, preventing proper operation of the auxiliary ventilation system. The circuit includes the auxiliary blower switch, associated wiring, connectors, and the HVAC control module that interprets the signal.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty or worn auxiliary blower switch
- Damaged, corroded, or loose wiring in the switch circuit
- Oxidized or bent pins in the auxiliary blower switch connector
- Auxiliary blower motor resistor out of specification
- Short to ground or voltage in the switch sense circuit
- HVAC control module internal failure in signal interpretation
- Blown fuse for the auxiliary blower circuit
3. Symptoms You Will Notice
- Auxiliary ventilation inoperative
- Erratic rear blower operation
- Incorrect climate control panel indicators
4. Step-by-Step Diagnosis
Check for blown fuses in the auxiliary blower circuit
Inspect the auxiliary blower switch and connector for damage, corrosion, or bent pins
Test the switch for proper continuity and resistance per manufacturer specs
Check wiring for shorts, opens, or high resistance between the switch and HVAC module
Verify the auxiliary blower motor resistor is within specification
If all else is good, suspect a faulty HVAC control module
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, it is generally safe to drive, but the auxiliary blower may not work, reducing comfort in rear seating areas. The main HVAC system should still function.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on the cause. A switch replacement may cost $50-$150, while an HVAC module can be $200-$400 or more.