I have a 2006 Ford F-150 pickup truck and when I switch the control from dashboard air circulation to defrost position, I get a squeaky rumble sound. The noise also occurs when switching to floor circulation from any other position. Any suggestions or explanations as to why this happens? – Paul
Positioned behind the truck's dashboard is the heating and air conditioning unit (HVAC) housing the heater core and air conditioning evaporator.
Also located within this unit is a series of air passages and doors that control the interior cabin temperature, fresh air recirculation and the panel mode control, which directs the air to the windscreen, foot well and dash vents.
These doors are controlled by actuators that respond to the driver's selection of temperatures and venting positions.
Since the noise occurs when you are choosing a venting position, let's focus on the panel mode system.
While not a technically challenging repair, access is tight. Typically, I locate and remove the suspected actuator, set it aside momentarily and first test the door mechanism to ensure all positions can be selected manually.
Once sure the door system is not binding, I move on to the actuator. The gears within are made of plastic and will deteriorate over time. An actuator replacement is common and far cheaper than a broken door as, in that case, the complete dash and HVAC unit need to be removed to service the doors.
Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing "Lou's Garage" in the subject area.
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