Peterbilt Medium Duty Trucks Operator's Manual after 1-07

Heating and Air Conditioning
NOTE: A cold compressor can cause refrigerant to
liquefy and warp the valve plates or cause a hydraulic
lock. Warm the engine before starting the air conditioner.
3. Set the air conditioner for maximum cooling.
4. Close all windows.
5. Idle the engine between 1000 and 1500 rpm and turn the
fan switch to High.
6. After the cab temperature cools to a comfortable level,
adjust the fan speed and other controls to keep the
desired condition.
Operating Instructions
If the air conditioner does not cool the air, have the
unit checked at an Authorized Service Center.
NOTE: When the air conditioner isn't in regular use,
operate it for at least 15 minutes at least once a
month or every 5,000 miles (8,000 km), whichever
comes first. This will lubricate the seals in the air
conditioning system.
– 42 – Y53-6008 Medium Duty (R10/06)