Bottom Line
Maintenance Tips
Don’t give your A/C the cold shoulder this winter

Special to Land Line Magazine

What’s the best kind of winter front? 
Take this quiz

In order to help their engines warm up faster, many drivers use winter fronts over their radiators. So what works best – a little hole in center or vertical lines?

If you said those that have vertical lines, you are right on the mark. A few years ago, engineers thought the best winter-front design was to have an opening in the center, right where the fan was, so it could provide unrestricted flow to the intercooler. We now know that this caused as many problems as it solved due to temperature differences across the radiator. 

The TMC Recommended Practice calls for the uniformly wide openings that run vertically across the entire width of horizontal flow radiators. This new design keeps heat more uniform in the radiator core. The differential expansion caused by the older designs led to numerous radiator and charge-air-cooler failures. 

by Paul Abelson, senior technical editor

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., which designs and manufactures heating, ventilation and air-conditioning units for Freightliner, Western Star, Mack, Peterbilt, Kenworth and other major heavy-truck suppliers.

The air conditioner removes excess moisture from the air, which helps the defroster quickly clear the wiper-stroke area and the door window glass, Hansen said.

“If there’s one thing you can do to improve the performance of your defroster – and to increase your margin of safety on a winter highway – it’s to make sure the A/C unit is functioning properly and is fully charged with refrigerant at the start of the heating season,” he said.

There are other steps truckers can take to troubleshoot defroster and cab heater complaints. Hansen said most are quick, simple and relatively inexpensive.

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 said. “If it’s a foam filter, wash it with warm water and dish soap.”

Valves: Check the heater’s water valves to make sure they open and close completely and that the actuator cables aren’t stretched. Remember 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,” said Hansen.

Blower motors: These 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 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 the A/C unit is critical to the efficiency of your defroster and heater in cold weather,” Hansen said. “Topping up the system with refrigerant and troubleshooting defroster and heater problems are preventive maintenance steps you can take now, before winter is at its worst.”

Aug/Sept Digital Edition