How to Troubleshoot A/C Problems in Freightliner Trucks

Freightliner AC systems are much larger than most vehicle systems, and they use a larger condenser and an air compressor to cool the air. An evaporator is used on freightliner trucks as a heat exchange medium to move the heat generated by the system away from the air conditioning unit. The most common problem with a freightliner AC system is a leaking compressor. A specially trained mechanic should fix any problems with the AC system, but you can troubleshoot to verify that there is a problem.

Step 1

Turn the engine on and allow the truck to warm up to its normal operating temperature. The water temperature gauge needle should sit in the center of the upper and lower marks on the gauge. Because most freighliners use the engine's pulley system to power the air conditioner, the truck must be at normal operating temperature before the AC will work at its best.

Step 2

Turn the fan speed on low and turn the AC to the coldest setting. Freightliners use a simple dial on the HVAC control unit to control the setting of the AC system. On a freightliner, the sound of the compressor starting is unmistakable. You should hear a low "hum" followed immediately by the cooling fan turning on. If you do not hear the compressor, it may have failed or is leaking. Either of these two scenarios will require that the compressor be replaced.

Turn the fan speed on the highest setting and set the AC to the coldest setting. If there is no cold air, the system needs to be recharged by a professional truck mechanic. The mechanic pumps refrigerant into the AC system so that the compressor has something to compress.