F21-1028-1381 | Genuine Paccar HVAC Climate Temperature Control Module

  Kenworth trucks

• Kenworth T680
• Kenworth T880
• Kenworth T660 (some configurations)

  Peterbilt trucks

• Peterbilt 579
• Peterbilt 567
• Other modern Peterbilt models with PACCAR HVAC systems

 1. Maintain desired temperature

• Lets you set a specific temperature
• The module automatically adjusts heating or cooling to keep it steady

 2. Control heating and air conditioning

• Turns the A/C system on/off
• Regulates heat from the engine (heater core)
• Mixes hot and cold air for the right balance

 3. Manage airflow and fan speed

• Controls how strong the air blows
• Adjusts fan speed automatically or manually

 4. Direct air where needed

• Sends air to:
  • Dashboard vents
  • Floor
  • Windshield (defrost)

 5. Improve driver comfort and safety

In vehicles like the Kenworth T680:

• Keeps the cab comfortable in all weather
• Prevents windshield fogging (defrost function)
• Reduces driver fatigue on long trips

 6. Enable automatic climate control

• Uses sensors (inside temp, outside temp, sunlight)
• Adjusts everything automatically without constant input

 7. Optimize system efficiency

• Prevents unnecessary A/C or heating use
• Helps reduce fuel or energy consumption

 1. Temperature won’t change

• Stuck blowing only hot or only cold air
• No response when adjusting temperature settings

 2. Fan/blower issues

• Fan not working at all
• Only works on one speed
• Fan speed changes randomly

 3. Airflow stuck in one position

• Air only comes from one area (e.g., defrost only)
• Can’t switch between vents, floor, or windshield

 4. A/C not turning on

• No cold air even when A/C is selected
• Compressor doesn’t engage

 5. Unresponsive controls

• Buttons, knobs, or touchscreen don’t respond
• Delayed or erratic response to inputs

 6. Intermittent operation

• Works sometimes, then suddenly stops
• May change behavior while driving

 7. Incorrect or fluctuating temperature

• Cabin temperature doesn’t match the setting
• Random hot/cold air swings

 8. Warning lights or fault codes

• HVAC-related error codes (in modern vehicles)
• Communication issues with other modules

 9. Electrical issues

• Blown fuses related to HVAC
• Burning smell (rare but serious)