Alternator Diagnostics & Replacement in Sunbury-on-Thames
The alternator keeps the battery charged and powers the car while running. When it fails, the battery drains and electrical systems start misbehaving.
We test the charging system to confirm the alternator is at fault before replacing it.
Common signs
Symptoms worth checking
- Battery warning light
- Dimming or flickering lights
- Flat battery after driving
- Whining from the front of the engine
- Electrical faults while driving
Testing the charging system
We measure charging output under load, check the regulator, wiring and belt, and on smart-charging cars review the data from the energy management system.
A failing alternator can flatten even a new battery.
What we check
- Charging voltage and current
- Regulator and communication
- Drive belt and pulley
- Wiring and grounds
What we can do
- Alternator replacement
- Pulley and belt replacement
- Wiring repairs
How it works
The process
- 01
Test charging.
- 02
Confirm fault.
- 03
Replace.
- 04
Verify output.
Why The Factory
Main-dealer capability, independent service
A Master Technician-led workshop with seven mechanical ramps, a dedicated MOT ramp and dealer-level diagnostics. Faults are shown to you and additional work is quoted before it goes ahead.
We stand behind the work we carry out. Parts and workmanship are covered in accordance with your statutory rights and any applicable manufacturer or supplier warranty. Please ask us for details relevant to your repair.
- Smart charging diagnostics
Free local collection & return
Available by arrangement within approximately five miles of our Sunbury-on-Thames workshop. Further afield? Just ask us.
FAQs
Alternator Repairs: your questions answered
What are the signs of a failing alternator?
Battery warning light, dimming lights, electrical faults and a battery that won’t stay charged.
Why has the battery warning light come on?
Usually a charging fault — alternator, belt, wiring or regulator.
Can a bad alternator flatten a new battery?
Yes.
How do you test a vehicle charging system?
We measure output under load and review charging data and wiring.
Can alternator problems cause electrical faults while driving?
Yes. Low voltage can affect many systems.
Related services
Battery Replacement
12V battery testing, replacement and registration where required.
Auto Electrical Repairs
Wiring, sensor, module and battery drain faults traced and fixed.
Starter Motor Repairs
Diagnosing clicks, slow cranking and no-start faults.
Need help with alternator repairs?
Send your registration and a quick description on WhatsApp, or call the workshop.
The Factory, Harris Way, Sunbury-on-Thames TW16 7EL