How to Test a Block Heater

by Dale Yalanovsky
itstillruns article image
the powerful engine image by kuhar from

A block heater is a built-in heating device to keep your engine block warm. This is especially useful in northern climes to give you almost instant heat during chilly morning start-ups, and block heaters are essential for any diesel-engine vehicle to aid in cold-weather starting. However, because they are encapsulated within the engine itself, the only external part will be a typical electrical cord and plug. But that by itself will allow you to test and see if your block heater is working.

Step 1

Plug in your block heater on a cold day. Wait one hour, then feel the engine block and compare the relative temperature of the block to other steel parts on the vehicle, like the bumper or the fenders. If the block heater is working, you'll notice a difference in the temperature between the engine block and the other parts of the vehicle.

Step 2

Unplug the block heater cord and pull it out and away from the vehicle. Make sure the vehicle is not running with the parking brake on.

Step 3

Set a multimeter to the "ohms" setting, then touch one probe to each of the prongs on the block heater plug and read the resistance. An ideal resistance reading will be about 20 to 30 ohms, but if there is a "0" or infinite resistance, the block heater is not functional.

More Articles

article divider