Battery/charging warning light
Battery light on; charging system fault or belt problem.
MEDIUM RISK
Common symptoms
- See page for quick checks
Cost expectations
Typical costs vary by car and region. Use this as a ballpark.
- DIY / parts: £20–£80
- Garage / labour: £80–£250
Most likely causes (ranked)
Start at the top. Rule out the common, cheap causes before expensive ones.
- Alternator output low
- Serpentine belt slipping
- Battery failing
- Wiring/ground fault
- Overrunning pulley issues
Quick checks (fast, low-cost)
Fast checks you can do with basic tools before buying parts.
- Measure voltage at battery (engine off and running).
- Inspect belt condition/tension.
- Check for corrosion at terminals/grounds.
- Scan for charging system codes (if supported).
- Listen for belt squeal.
Recommended tools
These tools make diagnosis faster and stop you buying random parts.
Related fixes
If your symptoms don’t match perfectly, check these next.
What to do next
- If voltage is <13.5V running, address alternator/belt.
- If belt is damaged, replace immediately.