At subzero temperatures, cars and trucks don’t like to start, especially if it’s colder than minus 20 degrees. To ensure starts on a cold winter mornings, vehicles in northern communities such as Whitehorse, Yukon are equipped with one or more electricity-powered heating devices which warm engine components and enable cold-temperature starts.

The most common type of heating device is a 750W block heater which is fitted into a casting hole on the engine block (warms the engine coolant / antifreeze). Oil pan heaters, consisting of a flat square pad approx. 4” by 4” glued to the bottom of the engine oil pan are also commonly used. In extreme cold environments, “battery blankets” are also used.

All three types of heating devices have an Achilles heel. Rather than using polar-grade electrical cords, the heating devices are typically fitted out with flat indoor grade cords. If flexed too often in sub-zero temperatures, the plug ends are prone to breaking off where the cord joins the plug. In accordance with Murphy’s law, this will usually happen on the coldest night of the year.

Anyone who has snapped off the cord end at minus 40 degrees while fumbling with mitts in poor light and then had to wire on a replacement plug end knows that the best solution to this problem is to avoid having the plug end snap off in the first place.

One solution is to isolate the heating device plug ends from all movement or flexing at cold temperatures. This Instructable explains how.

Step 1: Parts List

a) 1 outdoor extension cord, one metre (3.3 feet) long (fan tail as shown or inline type end)

b) 2 cable ties 20cm to 35 cm (8” to 14”) in length

Step 2: Find and Plug in Cord Ends

Pull out the cord ends for the electrical heating devices already installed in your vehicle and set them over over the grille.

Plug the heating device cord ends into the extension cord.

Step 3: Arrange and Secure Extension Cord

Arrange the cord inside the engine compartment taking care to “spread out” the cord as much as possible (that’s why a 1m cord or shorter is suggested).

Secure the extension cord inside the engine compartment using two or more cable ties.

If satisfied with the positioning of the extension cord, trim the cable ties.

Step 4: All Ready for Winter!

Place the cord end at the front of the vehicle and close the hood. Now you’re all ready for winter! When the cold temperatures hit, plug the cord end into a long extension cord connected to your house or parking lot receptacle. With the heating device cord ends fully isolated from movement you can be secure in the knowledge that your vehicle will be ready to go when you are.