This 2003 Ford Explorer XLT 4.0 came into the shop with a customer concern of a clicking noise in the center o,f the dash when he attempted to change the temperature from cold to hot. This vehicle has a manual HVAC control system. If he just barely moved the temperature knob, the noise would start. If he had the vehicle running and had the temp knob all the way to heat, the noise became louder.
This post is not so much a "how to", but rather a "why" post. It is not necessary to remove the entire dash to do this job; though, the service manuals call for that. I have found the job can be done by removing he center console and the cover beneath the steering column.
The issue is a common one on the Explorers around this year model. The culprit is a faulty temperature blend door actuator. Below is a picture of the actuator.
Internally, this actuator is made up of two small plastic gears. The piece that fails the majority of the time, causing this customer concern, is the smaller, black gear. If you take the actuator apart to see inside, you will see that this black gear has anywhere from two to three teeth sheered off of it. Below you will see the inside of the actuator and the black, plastic gear with the missing teeth.
Below is the small gear by itself. It may be hard to see, but in the pictures below, the two sheered teeth are at approximately the one o'clock position.
These missing teeth cause the gears to slip, not allowing the actuator to move the blend door to its proper location. When the gears hit this bare spot (the spot of the sheered off teeth) it cannot catch and so slips, causing the clicking noise in the dash.
We removed the faulty actuator and replaced it with a new OE actuator. We then tested the system, moving the temp knob from cold to warm and back several times. The noise was now gone and the blend door was operating properly.
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