How to jump-start a car in cold weather in Canada

To jump-start a car, connect the red cable to both positive terminals, attach the black cable to the donor battery’s negative terminal, then clamp the last black end to bare metal on the stalled car, away from its battery. Start the donor vehicle, wait, and then try the stalled one.

Cold snaps are when most Canadian drivers find out their battery is weak. Low temperatures slow the chemical reaction inside a lead-acid battery while thick, cold engine oil makes the engine harder to turn over. A battery that seemed fine in September can fail on the first sub-zero morning. Knowing the correct order for the cables protects you and your electronics.

The steps below follow guidance from Reader’s Digest Canada and the American Automobile Association. Your owner’s manual always takes priority, because some vehicles have designated jump-start terminals under the hood, and hybrids and electric vehicles often have specific rules.

Do not try to jump a battery that looks frozen, cracked or leaking, or one with bulging sides. Reader’s Digest Canada warns that a frozen battery can explode. Call roadside assistance or a tow service instead.

1. Check the battery and the manual. Confirm both batteries are the same voltage, usually 12 volts, and look for cracks, leaks or swelling. Check the owner’s manual for jump-start instructions specific to your vehicle.
2. Position the vehicles. Park the donor vehicle close enough for the cables to reach, but make sure the two vehicles do not touch. Put both in park (or neutral for a manual), set the parking brakes and turn off both ignitions, lights and accessories. Unplug anything in the power outlets.
3. Protect yourself. Wear safety glasses and remove rings or other jewelry. Batteries contain acid and give off explosive gas, so keep smoking materials and open flames well away.
4. Find the terminals. The positive terminal is marked with a plus sign and is usually larger than the negative terminal, which is marked with a minus sign. Clean away any snow or heavy corrosion so the clamps can grip.
5. Connect the red cable to the dead battery. Clamp one end of the red (positive) cable to the positive terminal of the weak battery. Keep the other end clear of the engine and body.
6. Connect the red cable to the donor battery. Clamp the other red end to the positive terminal of the good battery.
7. Connect the black cable to the donor battery. Clamp one black (negative) end to the negative terminal of the good battery.
8. Ground the last clamp. Attach the remaining black end to clean, bare metal on the stalled car, such as an engine bracket or bolt head, as far from the battery as possible. Do not use the dead battery’s negative terminal, because sparks there can ignite gas around the battery. Keep the cables away from belts and fans.
9. Start the donor vehicle. Let it run for several minutes to put some charge into the weak battery. Reader’s Digest Canada suggests about five minutes. AAA says at least one minute.
10. Try the stalled car. Crank the engine for no more than 20 seconds. If it does not start, wait about two minutes before trying again, as AAA advises. If it still fails after a few tries, stop and call for help.
11. Remove the cables in reverse order. Once the engine is running, disconnect the black clamp from the jumped car, then the black clamp from the donor, then the red from the donor, then the red from the jumped car. Do not let the clamps touch each other until all four are off.
12. Keep the engine running. Let the revived car keep running, ideally by driving it, so the alternator can recharge the battery. Have the battery and charging system tested soon, since a battery that failed once is likely to fail again.

If you do not have cables, a second vehicle or the confidence to do this yourself, call a roadside assistance provider. A portable jump-starter pack is another option, and it removes the need for a second vehicle. Follow the instructions that come with the unit.

To avoid a repeat, keep a set of cables in the trunk. Our guide to building a winter car emergency kit covers what else to carry, and our checklist for checking tire tread and pressure for winter and the piece on prepping wipers and washer fluid round out a cold-weather car check.

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Sources: Reader’s Digest Canada; AAA.