B2564 — Aux A/C Blower Speed 2 Circuit Short to Ground #

Note: The description for this code may vary depending on the vehicle manufacturer or Original Equipment Manufacturer (OEM).

• “A/C Blower Motor Speed 2 Circuit Low” (Ford)
• “Auxiliary Air Conditioning Blower Speed 2 Shorted to Ground” (GM/Chevrolet)
• “Blower Fan Speed 2 Output Short to Ground” (Chrysler/Jeep/RAM)

Summary of DTC B2564 #

The B2564 diagnostic trouble code (DTC) identifies a specific fault in the auxiliary air conditioning (A/C) blower motor’s speed control circuit—specifically, speed setting #2. In plain terms, this means the vehicle’s control module has detected that the wire or circuit commanding the second speed of the auxiliary blower motor is unintentionally connected (“shorted”) to ground. This can impact rear seat climate control, especially in vehicles with separate A/C controls for different cabin zones. While not immediately dangerous, this fault can reduce passenger comfort and might signal an emerging electrical issue elsewhere in the system.

If this code appears, it’s usually accompanied by a malfunctioning auxiliary blower, which could mean certain fan speeds aren’t working or the rear air system is unresponsive. Ignoring it may lead to further electrical complications if left unchecked, so prompt attention is recommended.

Common Symptoms for Code B2564 #

When B2564 triggers, you’ll likely notice some direct changes in the way your vehicle’s air conditioning system behaves—especially for rear passengers or anyone using the auxiliary A/C system. The symptoms may range from subtle annoyances to obvious failures, depending on the vehicle and severity of the short.

• Rear or auxiliary blower fan won’t work at speed setting #2
• Some or all rear fan speeds inoperative
• Blower runs only at one speed (usually high or low)
• Rear vents do not respond to speed changes
• Related A/C or HVAC warning lights illuminated
• Possible intermittent operation—works sometimes, fails other times

Probable Causes for Code B2564 #

In most cases, this DTC results from an electrical fault—think of it like a bridge allowing current to flow where it shouldn’t. The short to ground could be caused by frayed wiring, corrosion, or a failed relay. Here are the most common culprits, ordered from most to least likely:

1. Damaged or chafed wiring in the blower speed 2 circuit (insulation worn, wire touching metal bodywork)
2. Corroded or loose connector at the blower motor or control module
3. Faulty auxiliary blower motor resistor or speed control module
4. Relay stuck or internally shorted (if equipped)
5. Defective auxiliary blower motor itself (internal short)
6. Rare: Fault in the vehicle’s body control module (BCM) or HVAC control head

Step-by-Step Diagnosis for B2564 #

Diagnosing B2564 involves methodical electrical troubleshooting. You’re essentially playing detective—tracing the circuit, looking for clues where the current has wandered off course. Here’s the recommended approach for both DIYers and technicians:

• Read all stored and pending codes with a quality scan tool, and clear codes to see if the fault returns.
• Visually inspect the wiring harness between the auxiliary blower motor, relay (if used), and control module. Look for obvious damage, pinched wires, or corrosion.
• Locate and inspect all connectors in the circuit—unplug, check for bent pins, water ingress, or burnt contacts.
• Using a digital multimeter, test for continuity between the blower speed 2 wire and ground (with ignition off). Any continuity indicates a short.
• If possible, remove the blower resistor pack or control module and test for shorts to ground on the related output pin.
• Check the auxiliary blower motor for internal shorts by measuring resistance across its terminals and from terminals to ground.
• If all wiring and components test OK, use the scan tool to command the blower speeds and monitor live data for anomalies.
• Reassemble, road test, and verify repair by clearing codes and ensuring they do not return.

Possible Repairs for B2564 #

The right repair depends on the root cause—think of this as finding the leak before patching the pipe. Here’s what typically solves B2564:

• Repair or replace damaged wiring harnesses (tape, solder, or replace as needed)
• Clean, tighten, or replace corroded connectors
• Replace faulty auxiliary blower resistor or blower control module
• Replace defective relay (if present in circuit)
• Replace auxiliary blower motor if found internally shorted
• In rare cases, reprogram or replace the vehicle’s body control module or HVAC control head (professional diagnosis required)

Is It Safe to Drive With Code B2564? #

Yes, but with limitations. This fault will not typically compromise core vehicle safety or drivability. However, comfort may be reduced—especially for rear seat passengers, as the A/C system may not function properly in the back. If left unrepaired, electrical shorts can occasionally worsen, potentially leading to blown fuses or further HVAC system failures.

Vehicles Most Commonly Affected by B2564 #

While any vehicle with an auxiliary or rear A/C system can display this code, it tends to be more common in minivans, SUVs, and larger vehicles with advanced climate control features. Models with frequent reports include:

• Chevrolet Suburban / Tahoe / Traverse
• GMC Yukon / Acadia
• Ford Expedition / Explorer (with rear A/C)
• Chrysler Town & Country / Dodge Grand Caravan
• Honda Odyssey (select models with rear blower)
• Toyota Sienna
• Cadillac Escalade

Common Mistakes & Best Practices with B2564 #

It’s easy to overlook certain steps when chasing electrical issues—here’s how to avoid wasted time and ensure a solid repair:

• Don’t just replace the blower motor without confirming the short is not in the wiring.
• Always check connectors for corrosion, as moisture is a frequent culprit in rear HVAC faults.
• Test the circuit with the ignition off to avoid accidental shorts or further damage.
• Document wire colors and connector pinouts before disassembly—OEM wiring diagrams are invaluable.
• After repair, clear codes and check all blower speeds to confirm full system restoration.

Quick FAQ for Code B2564 #

Got questions? Here are some straight answers to common concerns:

• Q: Will replacing the fuse fix B2564?
  A: Only if a blown fuse was caused by a transient fault. If the short remains, the new fuse will blow again. Always fix the underlying cause.
• Q: Can this code drain my battery?
  A: Rarely, but if the blower relay is stuck “on” due to the short, it may cause the fan to run with the ignition off—potentially draining the battery overnight.

In summary: B2564 requires careful electrical troubleshooting, but with patience and the right approach, you can restore your A/C system’s performance and your cabin’s comfort. If you’re not comfortable chasing wiring faults, a professional auto electrician or OEM-trained technician can help.