In order to prevent heater core freeze-up during A/C operation, it is necessary to maintain permanent type antifreeze protection of +15°F (−9°C) or lower. A reading of −15°F (−26°C) is ideal since this protection also supplies sufficient corrosion inhibitors for the protection of the engine cooling system.
NOTE: The same antifreeze should not be used longer than the manufacturer specified.
For efficient operation of an air conditioned truck's cooling system, the radiator cap should have a holding pressure which meets manufacturer's specifications. A cap which fails to hold this pressure should be replaced.
Any obstruction of or damage to the condenser configuration will restrict the air flow which is essential to its efficient operation. It is therefore, a good rule to keep this unit clean and in proper physical shape.
NOTE: Bug screens are regarded as obstructions.
This is normally a single molded drain tube which expels the condensation, that accumulates on the bottom of the evaporator housing, into the engine compartment.
If this tube is obstructed, the air conditioning performance can be restricted and condensation buildup can spill over onto the vehicle's floor.