P1105
VWDual Alternator Upper Fault
Medium SeverityThis code indicates a problem detected in the upper circuit or control of the dual alternator system in your VW vehicle. This fault can lead to issues with the vehicle's electrical charging, potentially causing a dead battery or malfunctions of other electrical components.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before working on any electrical components to prevent electrical shock or damage to the vehicle's systems. Ensure the vehicle is on a level surface and engage the parking brake before starting any repair.
Common Symptoms
- Battery warning light illuminated on the dashboard
- Dim headlights or interior lights
- Difficulty starting the engine
- Malfunctioning electrical accessories
- Reduced vehicle performance
Common Causes
- Faulty primary or secondary alternator (upper circuit specific)
- Wiring harness open or shorted in the dual alternator control circuit
- Poor electrical connections at the alternator or control module
- Faulty alternator control module (if applicable)
- Engine Control Module (ECM) failure (less common, but possible)
Frequently reported on: Volkswagen Touareg (2004-2010), Audi Q7 (2007-2015), Volkswagen California/Multivan (T5/T6 generations)
Diagnostic Steps
- Inspect the battery and charging system for proper voltage using a multimeter.
- Visually check all wiring and connections related to both alternators, especially for the "upper" circuit mentioned, for signs of damage, corrosion, or looseness.
- Check the condition and tension of the serpentine belt(s) driving the alternators.
- Verify the alternator output voltage at idle and under load.
- Clear the code and retest to see if it returns immediately.
👨🔧 When to Call a Professional
If you lack specific diagnostic tools or expertise with dual alternator systems, or if the fault persists after basic checks, it is best to consult a professional Volkswagen mechanic.
Commonly Asked Questions
What does a "Dual Alternator Upper Fault" mean for my VW?
This code indicates an issue with the control or upper circuit of one of your vehicle's two alternators, which are responsible for charging the battery and powering electrical systems.
Can I drive with a P1105 code?
It's not recommended to drive for extended periods. The fault can lead to insufficient charging, potentially stranding you with a dead battery or causing other electrical components to malfunction.
Is this a difficult repair for a DIY mechanic?
Diagnosing an "upper fault" in a dual alternator system can be complex, often requiring specialized tools and a good understanding of electrical systems. It's generally considered an advanced repair.
What parts are typically involved in a P1105 repair?
The issue could be with one of the alternators itself, its voltage regulator, related wiring, electrical connectors, or potentially the alternator control module.
How can I prevent a dual alternator fault?
Regular maintenance, including checking battery health, inspecting serpentine belts, and ensuring electrical connections are clean and secure, can help prevent charging system issues.