Checking a Used Car's Electricals Before You Buy
A systematic walkthrough of every electrical system worth testing before you commit to a used car.
4 min read · Updated 14 Oct 2026
Key Takeaways
- Check the battery terminals for corrosion, and if possible, confirm the battery's age — most batteries last roughly 3-4 years, so an original or very old battery may need replacing soon regardless of current performance
- Test every exterior light individually (headlights on both settings, indicators, brake lights, reverse lights) plus the horn — a working set of lights is both a safety requirement and often indicative of generally well-maintained electricals
- Operate every power window fully up and down, test central locking from both the key and interior buttons, and check power mirror adjustment if fitted — slow or inconsistent window operation often signals a motor or regulator issue worth factoring into your decision
Electrical faults are among the most common post-purchase surprises in used cars, mainly because they are easy to skip checking in a quick viewing.
On This Page
1. Battery and Charging System
Check the battery terminals for corrosion, and if possible, confirm the battery's age — most batteries last roughly 3-4 years, so an original or very old battery may need replacing soon regardless of current performance.
2. Lights, Indicators and Horn
Test every exterior light individually (headlights on both settings, indicators, brake lights, reverse lights) plus the horn — a working set of lights is both a safety requirement and often indicative of generally well-maintained electricals.
3. Power Windows, Central Locking and Mirrors
Operate every power window fully up and down, test central locking from both the key and interior buttons, and check power mirror adjustment if fitted — slow or inconsistent window operation often signals a motor or regulator issue worth factoring into your decision.
4. Infotainment, AC Controls and Dashboard Warning Lights
Confirm the infotainment system powers on and responds to input, test AC controls across all settings, and note any dashboard warning light that stays on after startup — a light that does not clear needs an explanation before you proceed.
Frequently Asked Questions
Are minor electrical issues common even in well-maintained cars?
Yes, to some degree — the key is distinguishing a single minor fault from a pattern across multiple systems, which points to broader neglect.
Should a warning light that clears after a moment still concern me?
It is worth asking about regardless — some are momentary self-tests, but it is better to get a direct explanation than assume.
Is it reasonable to test the AC for an extended period during viewing?
Yes — running the AC for several minutes is a fair and common request, since cooling performance issues sometimes only show after sustained use.