Car Won't Start in Cold Weather? Here's Why and What to Do

# Car Won't Start in Cold Weather? Here's Why and What to Do

It's a freezing morning, you're already running late, and your car just won't start. Cold weather is tough on vehicles, but there are specific reasons why this happens and steps you can take to get going.

Why Cars Struggle in Cold Weather

1. Battery Power Drops

• Cold temperatures reduce your battery's capacity significantly:
• At 0°C, a battery has about 65% of its normal power
• At -15°C, it drops to around 40%
• At the same time, cold engines need MORE power to start

This double hit — less power available, more power needed — is why batteries fail in winter.

2. Engine Oil Thickens

Cold oil becomes thicker and more resistant to flow. This makes it harder for the engine to turn over and creates more resistance for the starter motor.

3. Fuel System Issues

• **Petrol cars:**
• Fuel doesn't vaporise as easily in cold
• Takes more cranking to get combustion

• **Diesel cars:**
• Diesel can "gel" in extreme cold
• Fuel filter can become blocked
• Glow plugs may fail to warm cylinders

4. Moisture and Condensation

Water can condense in fuel lines, battery terminals, and electrical connections. In freezing temperatures, this moisture turns to ice.

Quick Fixes to Try

For Battery Issues

• **Signs it's the battery:**
• Slow cranking
• Clicking sound
• Dim dashboard lights
• Nothing happens at all

Try this: 1. Turn off all electrical accessories (lights, radio, heater) 2. Turn the key to "on" (not start) for 30 seconds to prime the fuel system 3. Try starting with steady pressure — don't pump 4. If it almost catches, wait 30 seconds and try again

• **If you have jump leads:**
• Get a jump start from another vehicle
• Let it charge for 5-10 minutes before attempting
• Keep the engine running for at least 30 minutes after

For Diesel Cars

• **If diesel has gelled:**
• This requires warming the fuel system
• Try pouring warm (not boiling) water over the fuel filter
• Wait 10-15 minutes and try again
• Add diesel anti-gel additive when you refuel

• **Glow plug issues:**
• Turn key to "on" and wait for glow plug light to go off
• Repeat this 2-3 times to build more heat
• Then try starting

For Frozen Locks/Doors

• Use lock de-icer spray
• Warm the key with your hands or a lighter (carefully)
• Try a different door — they don't all freeze equally
• Never pour boiling water — it can crack glass

For Frozen Fuel Lines

• This is rare with modern fuel but can happen
• Move the car to a warmer location if possible
• A hair dryer on low can help (if near a power source)
• Wait for ambient temperature to rise

When to Call for Help

• Call a mobile mechanic if:
• Jump starting doesn't work
• Battery keeps dying immediately after jump
• Engine turns but won't fire
• You smell petrol (potential flooding)
• There are warning lights on
• Diesel appears to have gelled badly
• You've tried everything and it still won't start

Preventing Cold Weather Starting Problems

Battery Maintenance - Have your battery tested before winter - Replace batteries older than 4-5 years - Keep terminals clean and tight - Consider a battery blanket for extreme cold

Keep It Moving - Try to drive the car at least every few days - Short trips don't charge the battery fully - Occasional longer drives help maintain battery health

Use the Right Oil - Switch to winter-grade oil if you're in a cold area - Check your owner's manual for cold weather recommendations

Fuel Care - Keep the tank at least half full (reduces condensation) - Use winter diesel blends when available - Consider fuel additives in extreme cold

Park Smart - Park in a garage if possible - Face the car east so morning sun warms the engine - Use a car cover to reduce frost buildup

Cold Weather Emergency Kit

• Keep these in your car during winter:
• Jump leads or jump starter pack
• Torch with fresh batteries
• Ice scraper and de-icer
• Warm blanket
• Phone charger (12V)
• High-visibility vest
• Gloves

Get Help Now

Stuck with a car that won't start in the cold?

1. Open the Hault app 2. Select "Won't Start / Battery Issue" 3. Get matched with a nearby mechanic 4. They'll diagnose and fix the problem on-site

Whether it's a jump start, new battery, or something else — help arrives fast.

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*Hault connects you with mobile mechanics who can help wherever you are. Don't freeze waiting for help — download the app today.*