Modern cars are packed with electronics – and when they go wrong, the problems can be maddening. From phantom warning lights to complete system failures, electrical faults are one of the most common reasons for rejecting a used car.
Types of Electrical Problems
Dashboard warning lights are often the first sign of trouble. An engine management light could indicate various issues from minor sensor faults to serious engine problems. ABS or traction control lights mean a safety system isn't functioning correctly. An airbag warning suggests the restraint system has a fault – and all three of these are MOT failures. A battery or charging light points to alternator or battery issues, while multiple warnings appearing simultaneously often indicate a wiring or earth fault that's affecting several systems at once.
Sensor failures include parking sensors that don't detect obstacles, reversing cameras that show a blank or distorted image, rain sensors that won't activate the wipers properly, and light sensors that leave the headlights unresponsive. These might seem minor, but they affect both safety and the car's value.
Infotainment problems – screens that freeze or restart mid-drive, Bluetooth that won't connect, sat nav failures, audio cutting out, and Apple CarPlay/Android Auto issues – are increasingly common in modern cars that rely heavily on central touchscreens. If the car's main screen controls critical functions like climate or reversing camera, an infotainment failure can be more than just an inconvenience.
Electrical system failures cover central locking malfunctions, windows that won't operate, heated seats or steering that don't work, electric mirrors failing, and sunroof problems. Serious electrical issues are the ones that affect the car's fundamental usability: starting problems (no crank, or intermittent starting), battery drain leaving you with a flat battery overnight, wiring faults causing burning smells or intermittent failures, and water ingress damaging electronics throughout the car. If you're dealing with an electric car or hybrid, electrical systems are even more central to the vehicle – see our dedicated EV and hybrid guides.
Your Consumer Rights
Under the Consumer Rights Act 2015, all the car's systems – including electronics – must be of satisfactory quality and fit for purpose. Electrical faults that make the car unsafe, prevent normal use, cause significant inconvenience, or reduce the car's value all constitute breaches.
The strength of your case depends on the type of fault. Safety system failures (ABS, airbag, traction control), immobiliser or starting problems, persistent warning lights that would cause MOT failure, and water ingress causing multiple failures are strong grounds for rejection. Infotainment system failures, non-critical sensor failures, and convenience feature failures are potentially grounds for rejection depending on severity and whether they were advertised as working. Minor cosmetic electrical issues, features that were never promised, or problems disclosed before purchase make for weaker cases.
Within 6 months, electrical faults are presumed to have existed at purchase. This presumption is particularly valuable for electrical issues, which almost always develop gradually rather than appearing overnight.
Why Electrical Faults Indicate Pre-Existing Problems
Electrical problems don't usually appear from nowhere – they develop gradually, which is precisely why they're strong evidence of pre-existing issues.
Wiring degradation is the most common cause. Insulation breaks down over years, causing intermittent faults, short circuits, and corrosion at connections. This process is gradual – the deterioration was happening when you bought the car, even if symptoms only became noticeable afterwards.
Water ingress through blocked sunroof drains, damaged door seals, cracked windscreen seals, or failed HVAC drain tubes causes corrosion and electrical failures. The water entry point existed at purchase – water doesn't create its own path into a car overnight.
Poor previous repairs – incorrect wiring, damaged connectors, or badly installed aftermarket accessories – cause ongoing electrical problems. These were present when the dealer sold you the car, and a proper pre-sale inspection should have identified them.
Stored fault codes are particularly useful evidence. Modern cars record fault codes in the ECU, often showing when faults first occurred, how many times they've recurred, and related system data. A dealer should check fault codes before selling – and stored codes may prove issues existed well before your purchase date.
Think you might have a claim?
Check if you're entitled to a refund under the Consumer Rights Act. Free, takes 2 minutes.
Building Your Case
Get a diagnostic scan from an independent garage – ask them to read all fault codes, note when codes were first logged (if timestamps are available), identify patterns of recurring faults, and provide a written report. This is often the single most valuable piece of evidence for electrical fault claims.
Document every symptom in a log: what happens (warning light, system failure, etc.), when it happens (cold start, after a certain period of driving, intermittently), the date and mileage each time, and any patterns you notice. Video the dashboard when warning lights appear – intermittent faults are harder to prove, and footage captured in real time is compelling evidence.
Check MOT history for previous advisory items, electrical-related test failures, and warning light advisories. These can show that the car had electrical issues long before you bought it. And photograph everything – dashboard warning lights, system error messages, and physical signs of problems like corrosion or water damage.
What to Write to the Dealer
To: [Dealer]
Re: Rejection of Vehicle – Electrical Faults
Registration: [X]
Dear Sir/Madam,
On [date], I purchased [vehicle] from you at [mileage] miles for £[price].
Since purchase, the vehicle has exhibited the following electrical faults:
[List specific problems with dates and circumstances]
I have had a diagnostic check performed, which revealed [codes/findings].
These faults mean the vehicle is not of satisfactory quality under Section 9 of the Consumer Rights Act 2015:
-
Safety impact – [If applicable: The ABS/airbag/traction control warning indicates a safety system is not functioning correctly]
-
Fitness for purpose – [If applicable: These faults prevent normal use of the vehicle / affect the MOT status / make the vehicle unreliable]
-
Pre-existing condition – Electrical faults of this nature develop over time. [Reference any diagnostic evidence showing when faults were logged / evidence of water ingress / signs of previous problems]
[If within 6 months]: Under Section 19(14) of the Consumer Rights Act, faults appearing within 6 months are presumed to have been present at purchase.
I am rejecting this vehicle and require a full refund of £[amount].
Please respond within 14 days.
Yours faithfully, [Your name]
"It's Intermittent" – The Dealer's Favourite Excuse
Intermittent electrical faults are frustrating because they don't always appear when the dealer tests the car. But intermittent doesn't mean imaginary – many electrical faults are intermittent by nature, especially those caused by loose connections, temperature-sensitive components, or degraded wiring. You're still experiencing real problems, and the car still isn't satisfactory.
Diagnostic evidence helps enormously here: even if the fault isn't active during testing, stored fault codes prove it has occurred – and how often. The more documented instances you have (dates, videos, diagnostic records), the stronger your case becomes.
Recommended reading
MOT Implications
Certain electrical faults cause automatic MOT failure – illuminated warning lights (engine management, ABS, airbag), headlight faults, indicator issues, and brake light problems. If your car has failed or would fail its MOT due to electrical faults, you have particularly strong grounds for rejection. See our guide on car failed MOT after purchase.
Software Updates
Dealers sometimes claim a "software update" will fix electrical issues. Be cautious with this – software updates can fix some problems, but they don't resolve hardware failures like broken sensors or damaged wiring. Get written confirmation of exactly what the update addresses, and if problems persist afterwards, your rejection rights remain intact. A failed repair attempt – including a software update that doesn't resolve the issue – actually strengthens your position for rejection.
Finance Protection
If you used PCP, HP, or a credit card, contact the finance company alongside the dealer. They're jointly liable for the car's quality, often more responsive than evasive dealers, and can pursue recovery even if the dealer closes down.
When Rejection Might Not Apply
Feature Failures You Knew About
If the dealer disclosed that the sat nav didn't work and priced the car accordingly, you may struggle to reject for that specific issue.
Age-Appropriate Issues
Very old cars with some electrical quirks may be considered satisfactory given their age and price – though safety-critical systems should always work.
Aftermarket Modifications
If you've modified the car's electrical system, issues arising from those modifications aren't the dealer's responsibility.
The Bottom Line
Electrical faults can absolutely justify rejection, especially when safety systems are affected. Intermittent faults still count – document every occurrence. Diagnostic codes are powerful evidence because they show fault history with timestamps. Within 6 months, the law presumes faults were present at purchase, and the dealer must prove otherwise. Don't let them dismiss your claim with vague promises of software updates when the problem is clearly hardware.
Electrical faults plaguing your recently purchased car? Check if you qualify for our rejection service – we'll help you build your case.
Related Topics
