Frosty, Toasty or Roasty?

| April 07, 2005

The Four Keys
You need four things to keep the heat flowing in the winter.

  • The heater core must be clean and unclogged both inside and out and have a good flow of coolant through it.
  • The blower must circulate air as forcefully through the core and ducts as necessary, and its speed must be able to be regulated.
  • The mode doors must efficiently route air to the different outlets – allowing you to route the lion’s share of the air to the floor ducts for heating, but in mild, sunny weather, to route some of the air to the in-dash outlets.
  • The heater must have effective temperature regulation with either a temperature door or water flow regulating valve.

    What’s wrong, and what will fix it?

    1. Lack of heat:
    a.Do you have good coolant flow through the heater core? Check your cooling system maintenance manual. Service cooling system and flush water side of heater core, if necessary.
    b.Does the engine reach operating temperature? Check gauge, replace thermostat or seals as necessary.
    c.Does temperature door or water valve force full air or water flow through heater core? Repair/ replace cable or actuator motor, or water flow control valve.
    d.Do you have clogged filters, air ducts or core fins? Clean/replace filters, disassemble and vacuum out ducts or core fins, as necessary.

    2. Airflow does not shift to proper floor, dash or defrost outlet:
    a. Inspect ducting around door for obstructions.
    b.Check and adjust/repair cable clamps or cable.
    c.Inspect wiring to actuator motor and repair if necessary.
    d.Test and then replace actuator motor or in-dash controller
    (see text).

    3. Blower fails to operate in any speed setting:
    a.Test for voltage to motor. If non-existent, test/replace or repair wiring (including ground if used), fuse and dash switch. If voltage exists and ground is intact,
    replace motor.

    For Further Information Contact:

    Freightliner Corp.
    (503) 745-8000

    Peterbilt Motors Co.
    (940) 591-4000

    Kenworth Truck Co.
    (425) 828-5000

    International Truck and Engine Corp.
    (800) 448-7825

    (800) 499-6849

    Mack Trucks, Inc.
    (610) 709-3011

    Volvo Trucks North America
    (336) 393-2000

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