The electrical section of the MOT is narrower than people assume. It isn't a full electrical health check — it covers battery security and condition, visible wiring damage, the horn, and a specific set of warning lights that must not be illuminated.
The electrical section of the MOT is narrower than people assume. It isn't a full electrical health check — it covers battery security and condition, visible wiring damage, the horn, and a specific set of warning lights that must not be illuminated.
Wiring failures are usually about chafing and insecurity rather than anything not working. A loom rubbing on a suspension component will fail even if every circuit currently functions, because it's on its way to a short.
Here's the electrical wording that comes up most and what's normally behind it.
Battery insecure or leaking
The battery isn't held down properly, or it's leaking electrolyte. A loose battery can move about and short against the bonnet or bodywork, which is a genuine fire risk, and leaking acid damages everything it touches.
Full explanation of Battery insecure or leaking
Electrical wiring damaged, chafing or insecure
A section of the wiring is damaged, rubbing on something, or not properly clipped up. Note that the circuit can still be working perfectly — it's the condition and security that's being assessed, not the function.
Full explanation of Electrical wiring damaged, chafing or insecure
Horn not working or not suitable
The horn doesn't sound, is too weak, or makes a sound that isn't a continuous, uniform note. Two-tone air horns, sirens and musical horns are not acceptable on a road car and get recorded here too.
Full explanation of Horn not working or not suitable
How electrical defects are graded
Every MOT defect is recorded as dangerous, major or minor. Dangerous and major both fail the test; the difference is that a dangerous defect means the car is not roadworthy and must not be driven away. A minor defect passes but is recorded on the certificate, and an advisory is a note that something is wearing and will need attention before the next test. Tester notes in the electrical section use standard DVSA wording, which is why the phrasing on your certificate looks nothing like plain English — the pages above translate it.
Getting a electrical failure put right
You are free to take the car anywhere for the repair — there is no obligation to have the testing station do the work, and getting a second opinion on a big quote is sensible. Ask for the failed item to be shown to you on the ramp; a genuine defect is always something a mechanic can point at. Once repaired, a partial retest within ten working days covers the listed items without paying a second full test fee.
Avoiding it next year
Most electrical failures are found on a pre-MOT check for a fraction of the cost of a failure plus retest, because they are inspected before the clock is running. An MOT at Bob's Mechanical Repairs in Birnam, Dunkeld is £54.85, and anything found is explained and priced before work is agreed. Bob has 32 years on the tools, so the advice you get is what he would do with his own car.
Common questions
Can I drive away after a electrical MOT failure? Only if the old certificate is still valid and the defect is not dangerous. A defect recorded as dangerous means the car must not be driven on the road until it is repaired, and driving it can mean a fine and points.
Do I pay again for the retest? If the car is left at the testing station and the repair is done there, the partial retest is usually free. If you take it away and bring it back within ten working days, a partial retest is free for the listed items; after that a full test fee applies.
What does an advisory in this section mean? An advisory is a pass with a warning: the item is not bad enough to fail today but is wearing. Advisories on the same item two years running are the ones worth acting on before they become failures.
Decode your exact MOT wording or browse all MOT failure categories.