The rear defroster switch on some 2010 Chrysler 300s, Dodge Chargers and Jeep Grand Cherokees and Commanders with automatic temperature control (ATC) systems may be difficult to engage when pressed or may disengage once locked in place.
According to Chrysler, the problem usually occurs on vehicles built before Sept. 19, 2009, and it is the result of too much deflection in the ATC control head. Stiffening up the control head should eliminate the switch issue.
The illustration above shows the back of the ATC control head after removal from the vehicle. Look closely and you'll see two indentations with holes, as indicated by the arrows. Installing two specially made screws, part No.68078941AA, into these holes will stiffen the control head sufficiently to prevent the defroster switch from sticking against the sides of the bezel. After the screws are installed, just reconnect the wiring, reinstall the control head and confirm that the switch works properly.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via e-mail at [email protected].