SEATTLE, Wash. – Given the cold weather, your air-conditioning unit would seem to be an unlikely item for your truck’s winter prep checklist.

But it’s a matter of safety, says Red Dot Corp., which designs and manufactures mobile heating, ventilation, and air-conditioning (HVAC) units for Freightliner, Western Star, Sterling, Mack, and other major heavy-truck suppliers.

The HVAC system is integral to your truck’s windscreen defroster. The air conditioner removes excess moisture in the air, allowing the defroster to work more efficiently.

“If there’s one thing you can do to improve the effectiveness of your defroster, it’s make sure your air conditioner is functioning properly and is fully charged with refrigerant at the start of the heating season,” explains Gary Hansen, vice-president of engineering at Red Dot Corp. “You want to be confident that your defroster will clear ice and condensation quickly so you can be on your way.”

Hansen offers more ideas to ready your HVAC system for winter:

Turn on the defroster and run your hand under the dash, feeling for air leaks. Fill holes in the ducts with a compound or tape designed for heating systems.

Your heating system has at least one pleated paper or foam filter to capture dust, lint, carpet fibres, and other impurities that can clog the heat exchangers and reduce the efficiency of the heater system. Depending on the truck model, there will be one filter on the fresh-air inlet and another for recirculated air. The filter for the sleeper heating system is almost always for recirculated air and it’s accessible either through the toolbox or under the bunk.

“Most filters are reusable. If it’s a paper filter, simply vacuum the dirt away,” Hansen explains. “If it’s a foam filter, wash it with warm water and dish soap.”

Check your heater’s water valves to make sure they open and close completely, and that the actuator cables aren’t stretched. Have them replaced if necessary.

Blower motors get a workout in the winter. “On a cold morning, the motor goes from zero to full-speed in one swift turn of the knob,” Hansen says. “It’s not difficult to replace, so do it at the first sign of trouble.”

Check your cooling system for the proper glycol mix and wear on the hoses. Also look for signs of leaks, like bits of crystallized antifreeze on the radiator tank tubes, water pump, and other places where a hose attaches.

“It’s ironic, but your cooling system and A/C unit are critical to the efficiency of your defroster and heater in cold weather,” Hansen says.

“If you detect a drop in performance, contact a qualified mobile HVAC technician. Don’t wait until summer to fix the problem.”