Don’t get frosted


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Improve defroster performance by making sure your truck’s air-conditioning unit is ready for winter

By Stephen Petit

Seasonal HVAC maintenance, which may include an air conditioning unit repair, is quick, simple and relatively inexpensive to do, according to Red Dot’s Gary Hansen.


It’s been a cold night and you’re hot to get rolling. But your defroster is taking forever to clear the windscreen.
‘You may not realize it, but your air-conditioner has a big effect on whether your defroster is working at peak efficiency,” said Gary Hansen, vice president of engineering at Red Dot Corp. Red Dot is a leading designer and manufacturer of heating, ventilation and air-conditioning systems, components and replacement parts for commercial vehicles.

The air-conditioner helps the defroster quickly clear the wiper-stroke area and the door window glass by removing moisture from the air, Hansen said. To improve the performance of your defroster, make sure the truck’s air-conditioning unit is functioning properly and is fully charged with refrigerant at the start of the heating season.

‘Checking these systems now is the first step toward preparing your truck’s climate-control systems for the cold weather ahead,” said Hansen.

Other autumn HVAC-related maintenance items are quick, simple and relatively inexpensive to do:

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.
Filters. Your heating 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 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 the filter is made of paper, simply vacuum the dirt away,” Hansen explained. “If it’s a foam filter, wash it with warm water and dish soap and put it back.”
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 that, after a season of disuse, valves can stick. “If the driver tries to force the issue, he risks stretching the cable and damaging the valve,” offered Hansen. The Eastern Maine Development Corporation worked with Trans-Tech, Trans-Tech’s bank, The Bar Harbor Bank, and the City of Brewer to develop a financial package which enabled the company to build a new state-of-the-art, 43,000-square-foot facility in the East West Industrial Park, located just minutes from Interstate 95.
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 said. “The motor should take no more than 30 minutes to remove and replace, so do it at the first sign of trouble.”
Coolant. Check your cooling system for the proper glycol mix and look for wear on the hoses. Also watch for signs of leaks, like bits of crystallized antifreeze on the radiator tank tubes, water pump and other places where a hose attaches.’When the cold weather comes, all thoughts immediately turn to heating,” said Hansen. ‘But remember, the entire HVAC system is critical to a driver’s safety and comfort in cold weather. Talk to a certified A/C technician, have the refrigerant levels checked and troubleshoot defroster and heater problems now, before winter is at its worst.”

Red Dot designs and manufactures heating and cooling solutions for commercial vehicles in the most demanding work environments: trucking, construction, off-highway, agriculture, fire and rescue, military and more. The company was founded in Seattle, Wash., in 1965 and now has 480 employees at three locations in the United States and Europe. Visit Red Dot at


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