Winter MOT Preparation: 10 Things to Check Now
Cold weather exposes vehicle weaknesses. Prepare your car for winter MOT testing with these essential checks to avoid common seasonal failures.
Why Winter MOTs Are More Challenging
Cold temperatures, moisture, and road salt create perfect conditions for failures. Batteries weaken, fluids thicken, rubber perishes, and corrosion accelerates. Issues hidden in summer become obvious faults in winter.
Winter MOT failure rates run 15-20% higher than summer tests. Most failures are preventable with proper preparation. Start checking these items at least two weeks before your test date.
1. Battery Health and Charging System
Cold weather dramatically reduces battery capacity. A battery with 80% health in summer may fail to start reliably in winter, causing test day embarrassment.
Load test your battery
Most garages and parts stores test batteries free. Tests measure cranking amps and overall health. Replace if below 70% capacity. Batteries over 5 years old particularly vulnerable. Don't risk test day no-start.
Check alternator output
Engine running, battery voltage should read 13.8-14.4V. Lower readings mean weak alternator. Warning lights flicker or electrical issues worsen. Alternator failure leaves you stranded and causes MOT failures for warning lights.
Clean battery terminals
Corrosion on terminals reduces current flow. White or blue-green deposits indicate corrosion. Clean with wire brush and protect with petroleum jelly or terminal spray. Poor connections prevent reliable starting.
2. Lights and Electrical Systems
Lighting failures are the number one MOT fail category, accounting for 30% of all failures. Winter's shorter days mean more reliance on lights, increasing failure discovery.
Check every bulb
Test headlights (main and dipped beam), brake lights, indicators, fog lights, number plate lights, and reversing lights. One failed bulb causes instant MOT failure. Carry spare bulbs for quick roadside replacement.
Headlight aim and condition
Headlights must point correctly and emit white or yellow light. Moisture inside lenses causes MOT failure. Cloudy or yellowed lenses reduce output. Polish or replace lenses if degraded. Incorrectly aimed lights fail and endanger other drivers.
Dashboard warning lights
All warning lights must illuminate briefly at startup then extinguish. Permanent engine management, ABS, airbag, or traction control lights cause major failure. Diagnose and repair before testing. Electrical issues worsen in cold.
3. Tyres and Wheel Condition
Cold temperatures reduce tyre pressure by 1-2 PSI. Underinflated tyres wear faster and affect handling. Winter reveals tyre condition issues masked in warmer weather.
Tread depth verification
Legal minimum is 1.6mm across central three-quarters of tread. Check all four tyres. Replace at 3mm for winter safety. Worn tyres dramatically increase stopping distances on wet, icy roads. Use 20p coin test: if outer band visible, replace immediately.
Tyre pressure adjustment
Inflate to manufacturer's recommended pressure when cold. Check weekly in winter as temperature drops reduce pressure. Underinflation causes uneven wear and handling problems. Overinflation reduces grip. Door pillar sticker shows correct pressures.
Sidewall damage inspection
Check for bulges, cuts, or cracks in sidewalls. Winter potholes and curb strikes damage sidewalls. Any structural damage causes instant failure. Rotate tyres to inspect inner sidewalls. Replace damaged tyres immediately as blowout risk.
4. Brake System Performance
Brakes account for 10% of MOT failures. Winter moisture accelerates brake component corrosion. Squealing, grinding, or reduced performance needs immediate attention.
Brake pad thickness
Pads must have at least 1.5mm friction material. Visual inspection through wheels or professional measurement. Grinding noises indicate metal-on-metal contact. Replace pads in pairs per axle. Winter driving wears brakes faster.
Brake fluid condition
Fluid absorbs moisture over time, reducing boiling point. Dark or contaminated fluid needs replacement. Flush every 2 years as maintenance. Low fluid level indicates leak or worn pads. Spongy pedal feel suggests air in system or old fluid.
Handbrake effectiveness
Handbrake must hold vehicle on 1-in-4 gradient. Too many clicks to engage or won't hold suggests worn cables or pads. Cable corrosion common in winter. Professional adjustment or replacement needed. Electronic parking brakes need diagnostic check.
5. Wiper Blades and Washer System
Windscreen visibility is safety-critical. Worn wipers and empty washer bottles cause failures. Winter conditions expose wiper inadequacy quickly.
Wiper blade replacement
Replace blades if they smear, chatter, or leave streaks. Winter conditions perish rubber faster. Blades should clear windscreen in single sweep. Test on wet screen. Replace annually or when performance degrades. Cost only £10-20 per pair.
Washer fluid and jets
Fill with proper screenwash concentrate, not just water. Water freezes and damages system. Check all jets spray onto windscreen and rear window. Clear blocked jets with pin. Replace if damaged or misaligned. Inadequate washing causes MOT failure.
6. Suspension and Steering Components
Winter potholes and deteriorated roads stress suspension. Worn components affect handling and safety, causing MOT failures.
Shock absorber condition
Press each corner of car and release. Should bounce once and settle. Multiple bounces indicate worn shocks. Oil leaks on shock bodies mean failure. Worn shocks increase stopping distance and reduce stability. Replace in pairs per axle.
Ball joints and bushings
Listen for clunking over bumps or when turning. Play in ball joints or worn bushings cause failure. Professional inspection recommended as difficult to check yourself. Worn components dangerous and worsen quickly. Winter potholes accelerate wear.
7. Exhaust System and Emissions
Cold starts reveal exhaust problems. Road salt accelerates corrosion. Emissions must meet standards for vehicle age.
Exhaust leaks and corrosion
Inspect entire exhaust system for holes, corrosion, or loose brackets. Leaks before catalytic converter cause emissions failure. Loud exhaust noise indicates problems. Road salt damages exhausts faster in winter. Professional inspection recommended.
DPF and emissions systems
Diesel vehicles must have functioning DPF. Warning lights or excessive smoke cause failure. Short winter journeys prevent DPF regeneration. Take occasional motorway drive to clear filter. Tampering or removal results in instant failure and possible prosecution.
8-10. Final Essential Checks
Windscreen condition
Chips larger than 10mm in driver's view area or 40mm elsewhere cause failure. Cracks of any size in swept area fail. Winter temperature changes make chips spread rapidly. Repair small chips before they crack. Insurance often covers repair without excess charge.
Doors, bonnet, and boot
All must open, close, and secure properly. Hinges and latches functioning correctly. Bonnets must stay open safely for testing. Boot must close flush. Frozen or stiff locks should be lubricated. Adjust if needed.
Number plate legibility
Plates must be clean, undamaged, and correctly spaced. Winter road grime obscures plates quickly. Damaged or non-reflective plates fail. Check front and rear plates. Replace if faded, cracked, or incorrect font. Costs only £10-15 for new plates.
Pre-MOT Checklist Summary
- ✓ Battery load tested and terminals cleaned
- ✓ All lights working and aimed correctly
- ✓ Tyres above 1.6mm tread, correct pressure
- ✓ Brakes effective with sufficient pad material
- ✓ Wipers clear screen, washer system full
- ✓ Suspension components tight and quiet
- ✓ Exhaust leak-free, emissions within limits
- ✓ Windscreen chip-free in critical areas
- ✓ Doors, bonnet, boot operate smoothly
- ✓ Number plates clean and legible
Book Your MOT Early
Don't wait until expiry day. Book 2-4 weeks early to allow time for repairs. If you fail, you have remainder of current MOT to fix issues and retest. Testing on expiry day risks driving without valid MOT if you fail.
Choose reputable garage with modern testing equipment. Read reviews and compare prices. Some offer free retest within 10 working days. Quality garages explain failures clearly and suggest economical repairs.
Check When Your MOT Is Due
Don't let your MOT expire this winter. Check your current expiry date and book your test in advance.
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