“Wiper blade deteriorated”
The cheapest thing that will ever appear on your MOT certificate, and the only one on the whole list you should genuinely do yourself. Ten pounds, ten minutes, no tools.
The rubber on a wiper blade has hardened, split or worn, so it smears rather than clears. That is the entire problem, and the entire solution is a new blade.
Do it before the next time it rains properly. There is no mechanical consequence to waiting, only a visibility one.
Per blade, bought from any motor factor or supermarket. You do not need a garage for this, and most parts shops will fit it free while you wait.
If a wiper blade appears on a repair quote at forty pounds, read the rest of that quote twice.
A wiper blade is a strip of rubber held against curved glass by a sprung frame. It works by presenting a sharp edge to the screen and flipping over at each change of direction. When the rubber hardens with age and ultraviolet light, or the edge wears round, it stops flipping cleanly and starts pushing water around instead of clearing it. That is what smearing is, and it is what the tester saw.
What the tester actually checks
That the wipers work. Both front wipers must operate, and on the speeds the car was built with. A wiper that does not move, or moves only on one setting, is a fault rather than an advisory.
That they clear the screen effectively. This is where blade condition comes in. The test is about the swept area being cleared well enough to give the driver an adequate view, not about the blade looking new.
That the washers work and reach the screen. Wipers and washers are assessed together, because clearing a dirty screen needs both. An empty washer bottle is a common and entirely avoidable failure — fill it before the test.
That nothing is missing or insecure. A blade hanging off its arm, a missing blade, or an arm that has come loose all count.
What the tester is not doing is judging cosmetics. A blade with a scruffy-looking rubber that still clears the screen properly passes without comment. The advisory means yours left marks.
When wipers fail an MOT
A wiper fails when it does not clear the screen adequately, when it does not operate, or when the blade or arm is insecure or missing. Deterioration that still leaves an adequate view is an advisory — which is what yours is.
There is no measurement and no age limit. The assessment is functional: the tester operates the wipers with the screen wet and looks at the result. That makes it one of the more objective judgements in the test, because a smear either obstructs the view or it does not.
The washers are the trap. Failing to deliver washer fluid to the windscreen is a failure in its own right, and it catches people out because nobody thinks of the washer bottle before an MOT. It is also the single cheapest failure to prevent.
The rear wiper counts where one is fitted. If the car has a rear wiper it is assessed on the same basis as the fronts, and it is easily forgotten because most people rarely use it.
Doing it yourself
This is the one item on any MOT certificate where the honest advice is not to pay anyone.
Getting the right blade. Every motor factor and supermarket has a lookup by registration or by make and model, online or at the counter. Front blades are usually different lengths on driver and passenger sides, so check both figures rather than buying a pair of the same.
Fitting. Lift the arm away from the screen until it locks upright, press the release tab on the connector, slide the old blade off and the new one on until it clicks. Most blades come with the correct adaptor already fitted. Lower the arm gently rather than letting it snap back — a returning wiper arm can crack a windscreen.
If you would rather not, most parts shops fit blades free while you wait, and any garage will do it in a couple of minutes. What you should not do is have it added to a repair bill as a line item with labour attached.
While you are there: top up the washer bottle and check the jets are aimed at the screen rather than over the roof. Both are free and both are MOT items.
What it costs
£8–£25 per blade. Budget blades work perfectly well for a season or so. Mid-range blades from an established brand last longer and are quieter, and the difference in price across two blades is smaller than most people’s weekly coffee.
Flat beam blades versus conventional. Newer cars use single-piece beam blades that press evenly along their length; older cars use framed blades with multiple pivots. Fitting a beam blade to a car designed for framed ones usually works and often improves the wipe, but check the fitting type before buying.
What makes blades last longer is unglamorous: keeping the screen clean, never running them dry on a dusty screen, and lifting them off the glass in freezing weather rather than tearing frozen rubber off ice. Most blades die from being used on ice or grit rather than from age.
This is also the one advisory where our usual advice to compare garage quotes simply does not apply. Fix it yourself and spend the attention on whatever else the tester wrote down — our advisory checker decodes the rest.
Wiper advisory — your questions
When do wiper blades fail an MOT?
When they do not clear the screen well enough to give an adequate view, when they do not operate, or when a blade or arm is insecure or missing. Deterioration that still leaves an adequate view is recorded as an advisory instead. There is no age limit and no measurement — the tester wets the screen and looks at the result.
How often should wiper blades be replaced?
Roughly once a year is the common recommendation, though it depends far more on use and storage than on time. Cars parked outside in strong sun degrade blades faster, and running wipers on a dry or gritty screen wears the edge quickly. Replace them when they smear rather than by the calendar.
Can I replace wiper blades myself?
Yes, and this is the one MOT item where you genuinely should. Lift the arm until it locks upright, press the release tab, slide the old blade off and the new one on until it clicks. No tools. Lower the arm gently rather than letting it spring back, since a returning arm can crack the screen.
Why do my wipers smear even with new blades?
Usually the screen rather than the blade. Traffic film, polish residue, wax from an automatic car wash or tree sap leave a coating that new rubber cannot clear. Cleaning the glass properly with a dedicated glass cleaner, then wiping the blade edge with a damp cloth, fixes most cases. Worn wiper arm springs are a rarer cause.
Are expensive wiper blades worth the money?
Mid-range blades from an established brand generally last longer and run more quietly than the cheapest available, and the difference across two blades is a few pounds. Beyond mid-range the returns diminish quickly. This is not a component where the premium option changes anything meaningful about how you drive.
Does the rear wiper count in the MOT?
Yes, where one is fitted. It is assessed the same way as the fronts — it must work and clear its swept area adequately — and it is easily forgotten because most drivers rarely use it. The rear washer counts too, so check it delivers before the test.