Car won't start in the cold

Listen before you do anything

On a minus 25 morning in Ottawa, a car that will not start is usually telling you what is wrong by the sound it makes. Before you call anyone, turn the key or press the button once and pay attention. Then look at the dash lights while you do it.

The four common outcomes are below, roughly in order of how often they come up in January.

Rapid clicking

A fast clicking or chattering from under the hood, with the dash lights dimming or flickering, almost always means a weak battery. There is enough power to pull in the starter solenoid, but as soon as the starter tries to turn the engine, the voltage collapses and the solenoid drops out. It does this over and over, which is the clicking.

This is the case where a boost usually works. If it starts on a boost, do not assume the problem is solved. Either the battery is near the end of its life, or something drained it overnight, or the alternator is not charging it back up. A battery test checks all three.

Slow, labouring crank

The engine turns, but slowly, like it is wading through mud. It may catch after a few tries or it may not.

Cold makes this worse from both sides. The battery puts out less in the cold, and the engine oil is thicker, so the starter has to work harder. A battery that cranked fine in October can be right on the edge by the first deep cold snap. Corroded or loose cable ends do the same thing, because they choke the current between the battery and the starter.

If it does start, let it run and drive it for a good while, not two minutes to the corner store. Short trips in the cold use more charge than they put back.

One click, or nothing at all

A single solid click, with the dash lights staying bright, points away from the battery and toward the starter, the starter relay or a bad connection at the starter. Some starters will work after a few tries and then quit for good.

Complete silence with no dash lights at all is usually a completely flat battery or a cable that has come off. Silence with normal dash lights can be the starter, the ignition switch, the gear selector not being fully in park, or the car not recognising the key. Try neutral, and try the spare key if you have one.

It cranks normally but won’t fire

If the engine spins at a normal speed but never catches, the battery and starter are doing their jobs. The problem is fuel, spark or the security system. In deep cold, water in the fuel can also freeze in a line. Keeping the tank above a quarter through the winter helps, because there is less room for condensation inside it.

Do not keep cranking for minutes at a time. You flatten the battery and can overheat the starter. A few tries of about ten seconds with a rest between is plenty. After that, it needs a diagnosis, not more cranking. See car won’t start for what we check.

Battery CCA and the minus 25 test

Every battery has a cold cranking amps rating, printed on the label as CCA. It is the current the battery can deliver at minus 18 degrees Celsius for 30 seconds while staying above a set voltage. On a much colder Ottawa morning, the real output is lower again.

That is why the cheapest battery that fits is a poor choice here. Match or beat the CCA of the original. Most batteries last a few years, and if yours is older than that and slow to crank, it is a good time to have it load tested before the real cold arrives.

Block heaters

A block heater warms the engine coolant overnight, so the oil is thinner and the engine turns over more easily. On very cold mornings it makes a real difference to how hard the battery and starter have to work, and you get heat in the cabin sooner.

Most people plug in with an outdoor timer set to come on a few hours before they leave, rather than all night. If your car has a plug tucked behind the grille, it already has one. If the cord is damaged or the heater does not warm up, get it checked before January.

How to boost a car safely

Before you start, look at the dead battery. If the case is cracked or bulging, or you think the battery has frozen, do not boost it. A frozen battery can rupture.

Then, with both cars off:

• Red clamp on the positive terminal of the dead battery.
• Other red clamp on the positive terminal of the good battery.
• Black clamp on the negative terminal of the good battery.
• Last black clamp on bare, unpainted metal on the dead car’s engine or a ground point, away from the battery.

Start the good car and let it run a few minutes, then try the dead one. Once it starts, remove the clamps in reverse order. If your owner’s manual shows dedicated boost points under the hood, use those.

If it still won’t go

SA Auto Repair does not tow. If the car will not start, arrange a tow to Unit 1, 1541 Star Top Road, Ottawa, ON, just off Highway 417 Exit 112 at Innes Road, or call (613) 744-1521 first so we know it is coming. If you can get it running on a boost, you can drive it in and book online under car won’t start or battery, with a note about what it did that morning. A yearly tune up in the fall is also a good time to have the battery and charging system looked at before winter.