It's Winter. Don’t Give Your A/C the Cold Shoulder

Who runs the A/C in the middle of winter? You do—if your truck or equipment cab has a defroster.

Your air conditioner removes excess moisture from the air, so it has a big effect on how quickly and effectively the defroster can clear the windshield. “If you want to improve the performance of your defroster and increase forward visibility for your drivers or equipment operators, have your air conditioner inspected before winter,” says Gary Hansen, vice president of Red Dot Corp. Based in Seattle, Red Dot designs and manufactures heating and air-conditioning systems, components, and replacement parts for heavy trucks and other commercial equipment.

There are other steps you can take to prepare for cooler temperatures, Hansen says. Most are quick, simple, and inexpensive:

1. FILTERS Your HVAC system has at least one pleated paper or foam filter to capture dust, lint, carpet fibers, and other impurities that can clog the heat exchangers and reduce the efficiency of the heater system. Depending on the type of vehicle, there will be one filter on the fresh-air inlet and another for recirculated air. If the truck has a sleeper, 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.

”Dirty filters can restrict air flow and allow dirt and dust to interfere with the evaporator core,” says Hansen. Most manufacturers recommend checking the filter every three months and replacing it with a filter that meets the original-equipment spec.

2. DUCTS 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.

3. VALVES Check the heater’s water valves to make sure they open and close completely and that the actuator cables aren’t stretched. Remind drivers and equipment operators that valves may be sticky after a season of disuse. “If the you try to force the valve to open or close, you risk stretching the cable and damaging the valve,” says Hansen.

4. BLOWER MOTORS 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. “The motor should take no more than 30 minutes to remove and replace, so do it at the first sign of trouble.”

5. RECEIVER DRYER The receiver-dryer contains desiccant, a chemical that attracts and traps moisture. When desiccant becomes saturated, moisture in the system is free to combine with refrigerant and turn into corrosive hydrofluoric acid. The receiver-drier should be replaced once a year, and the sight glass on the moisture indicator checked every time you change the oil or perform scheduled maintenance. A blue dot means the refrigerant is dry; pink, white, or grey indicates acid or moisture in the system.

“It may seem odd that the air conditioner is so critical in cold weather,” Hansen says, “but it reinforces the need to see a qualified A/C service technician at regular intervals during the year, not just during hot weather.”