Heat vents no longer work properly

By Doug McAllister

Q. I have a 2006 Ford Explorer and all of the sudden the heat will only come out the defrost vents no matter what I do. It does not matter what position I put the (heater selection) knob in, there is still no change. Do you have any ideas?

A. I believe your vehicle has a combination of vacuum- and electric motor-controlled blend doors. I would have to see it to know for sure what has failed, but it sounds like you may have lost vacuum to the controller.

We have seen this before where a vacuum hose under the hood gets cut or detaches. It is also common on the Fords for the mode control motors to go bad, or the nylon gears that move the blend doors will give out.

Sometimes you can tell it's a gear failing because you hear a rhythmic clicking underneath the dashboard when trying to control the temperature direction or the mode.

Some of those gears are fairly easy to get at and others require extensive dash disassembly to replace them. Good luck and I hope it is as simple as replacing a vacuum hose.

• Douglas Automotive is at 417 W. Main St., Barrington; 123 Virginia Road, Crystal Lake; and 416 Northwest Hwy., Fox River Grove. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.