Why your car won't start in cold weather

Battery, starter motor, alternator — diagnosing the three before replacing one.

A car that starts fine in summer but won’t start in winter has one of three problems: battery, starter motor, or alternator. We diagnose all three before replacing one.

Battery — the usual suspect

Cold reduces battery capacity by 30–50%. A battery that was barely enough in October is dead in January.

Symptoms:

• Cranking is slow, lights dim
• Click-click-click when you turn the key (relays trying to engage but battery can’t deliver current)
• Dashboard goes dim under cranking

Fix: battery test (we can come to you — mobile mechanic €80) and replace if dead. €110–€180 for a quality 3-year-warranty battery. We code the new battery to the BMS where required (most VAG, BMW, Mercedes after 2010).

Starter motor

If the battery tests good but the engine still won’t crank, suspect the starter motor.

Symptoms:

• Single click when you turn the key, no cranking
• Sometimes intermittent — works on second or third try
• Cranking sounds slower than usual but battery is fine

Fix: starter motor replacement, €150–€350 depending on access.

Alternator

If the car starts on a jump but kills the battery again within a few drives, the alternator isn’t charging.

Symptoms:

• Battery warning light on dashboard
• Dim headlights at idle
• Battery dead the morning after a fresh charge

Fix: alternator replacement, €250–€500. We test for charge output before replacing — sometimes it’s just a worn drive belt slipping.

What to do

Don’t replace one of the three on a guess. Diagnostics takes 30 minutes and tells you which one — saves you the cost of replacing the wrong part.

Phone 01 847 5146 — same-day diagnostic slots Mon–Wed.