Troubleshooter: What is a block heater and why should Canadian vehicles have one

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Winter-driven Canadian vehicles need block heaters, no matter what carmakers and their sales reps tell you. Many dealership consultants think engine block heaters are old-hat, that modern advancements in design and build have rendered them obsolete; Mother Nature not-so-politely disagrees. When the outside overnight temps dip to below -25° C, both new and old vehicles can refuse to start themselves — at least unless they have some outside help.

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Engine block heaters are essentially just a water-heater element that look and operate just like the units that warm water in your home’s basement. They’re mounted in a hole in the engine’s lower block (hence their name) and live submersed in the liquid coolant. Most could fit in the palm of your hand before installation and are powered by normal 120V household electrical current via a purpose-made cord — the sort you’ve likely noticed poking out from the corner of some vehicles’ hoods. These warm the engine coolant by just a few degrees, and heat transfer also warms the engine oil. Plug one of these in for a few hours, then put a hand on the engine block and you should find it warm to the touch, but never hot.

Do block heaters drain your battery?

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Block heaters are powered directly by your household outlet, so they won’t discharge your vehicle’s battery. Mounted in the bottom of the cooling system, these are completely submerged so they won’t burn themselves out. Likewise, block heaters don’t present any danger to the engine as they can’t overheat things, and as their circuits are safely grounded, they won’t present any risk to home outlets or properly rated extension cords. You can leave a block heater plugged in indefinitely, and as most are rated at around 1,500 watts, their impact on your utility bill should be about the same as using a hair-dryer.

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How long does a block heater take?

How long a block heater takes to do its job depends on the engine size and the outdoor temperatures. Smaller four-cylinder units may only need a few hours of heater operation (made easy with an outdoor outlet timer), while larger V8s and diesels usually need to be plugged in overnight.

Benefits of using a block heater

Block heaters almost guarantee an easy startup, providing the vehicle’s battery is in good condition (you did get it tested this past fall, didn’t you?). Secondly, as the engine coolant is the source of your vehicle’s HVAC system heat, pre-warming it with a block heater means near-instant warmth from the vents. It will also improve fuel economy, as the faster an engine reaches full operating temperature, the faster the fuel injection system will lean out to use less fuel.

It used to be common for all vehicles sold in Canada to have a block heater as standard equipment, but sadly that’s no longer the case. Even pickups and large SUVs don’t always come with them from the factory, and the number of makes and models that can’t accept block heaters seems to grow every year. Block-heater kits average around $100 for the part, but installation can vary wildly depending on what location is permitted on the engine and what (if anything) needs to be removed to access it.