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It’s A/C Checkup Time

By on May 1, 2016
HH-AC

Stay cool and avoid costly system failures

Your A/C system is out-of-sight and typically out-of-mind during most winters until ambient temperatures rise. Don’t be disappointed when you move those controls to the blue or cold setting. Hopefully, the A/C compressor engages and the air streaming from the dash vents feels cold. Unfortunately, the compressor may not be up to the task, may not engage at all, or may deliver less than stellar results.

To add insult to injury, an under-performing compressor is typically suffering a slow death from a lack of refrigerant that must be returned from the cold side of your A/C system. Focusing on a checkup and any critical maintenance now will help ensure a cold A/C system and long compressor life. Four important components or systems must be in good working order: the cabin filter, refrigerant level, condenser, and cab duct/blend air doors.

Often, cabin filters are not adequately maintained, because they have no gauge and typically are not visible. You may not even know how and where to gain access. If a truck’s cabin filter is dirty, the A/C system will likely freeze up and prevent needed refrigerant from reaching the compressor. This quickly destroys the compressor and sends metal shavings throughout the system. At the start of a new A/C season, check your filter and replace it, if necessary. If you travel in dusty or dirty climates, your cabin filter needs service or replacement more often.

Most of today’s trucks utilize R134a refrigerant. It has a very tiny molecular structure, which makes the modern A/C system more prone to leaks than decades-old systems. Consequently, the refrigerant charge must be monitored and maintained. Truck manufacturers have substantially reduced the amount of refrigerant, making even a small leak a potentially huge problem. Short term, it can sometimes be camouflaged by the improved performance provided by added refrigerant, causing a driver to overlook the risk of a freeze up. In fact, an A/C system that periodically freezes up is usually telling you that it needs to be checked for leaks, repaired and refilled properly—now!

The condenser mounted in front of the radiator must be clean and the airflow must be able to hold a dollar bill in place against the front of the condenser. Insects, mud, pieces of plastic bags and any other airflow restrictions across the condenser must be removed. The condenser is a heat exchanger that must be able to remove the heat absorbed by the cold refrigerant as air circulates inside the cab of the truck, allowing the heat to escape into the atmosphere. When airflow is restricted, heat remains in the refrigerant and eventually reaches the compressor, resulting in its slow death. Use a mild cleaning agent such as Simple Green, and spray it off with a water hose. Even a small amount of dust, that is almost invisible to the eye, will reduce condenser efficiency.

Finally, modern trucks have A/C systems controlled by one or more computers. One system that the computer(s) must control properly is the directional doors inside the dash and floor panels that direct the airflow to the designated location such as defrost, floor and the center ducts. These later model trucks use a blend-air system that enables the heater and air conditioner to run at the same time. Engineers design these systems to allow a precise temperature to be achieved by blending hot and cold air, measuring the resulting temperature, and starting the cycle over again.

A computer controls the blend-air door, thereby obtaining the desired cab comfort level. A door that is out of calibration may not respond to a command or may respond in an unacceptable manner. The good news is—most of the time—it is easy to recalibrate the door by following some simple steps. Check your operating manual or take your truck to a qualified technician for this important recalibration.

So, remember to service that filter, have your refrigerant level checked, identify and repair leaks, clean the condenser, and recalibrate the blend-air doors. TA Service Centers have the equipment and expertise to help you with your 2016 A/C system checkup. It will keep you feelingHomerHogg cool for those long, hot summer days ahead.

Homer Hogg’s Maintenance Matters airs on the Dave Nemo Show (Road Dog Trucking, SiriusXM 146), 8 a.m. ET, the first and third Thursdays of each month.

Homer Hogg, Technical Development Manager for TA and Petro, has worked as a truck technician for more than 30 years. He is ASE Master-Certified, a Daimler Certified Trainer, and a member of the Nashville Auto-Diesel College Hall of Fame.

 

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