My wife reports a new problem. The windows (all windows, not just the windshield) will fog up. They can be cleared by setting the control panel to defrost, but she swears this was never necessary before.
I am at a loss to understand how the automatic climate control would know when defrost was necessary. Looking at the manual, the system has a sunlight sensor, passenger compartment temperature sensor, and outside temperature sensor. Perhaps there is some combination of inside & outside temperature that causes the defroster to come on????

Since this affects all windows, I don't think the problem is the heater core. There are no flashing lights on the climate control to indicate a fault.

Hi Peter,

If the heater core were leaking or seeping, you would not see a warning light, until the coolant level in the expansion tank dropped low enough. While I'm not saying that it is definitely your core, I would mention that foggy windows (all windows) is a strong sign that the core may be at fault, as the blower would be acting as a humidifier, due to a leak, and the moisture would be distributed throughout the car. Also if the ECC has a mechanical issue, it might not be allowing fresh air into the cab (stuck in re-circulate mode).

My .02

BB

I'm kind of leaning toward the "stuck in recirculate mode" theory. The reason I don't think it is the heater core is that turning the setting to "defrost" clears the windows. If it were a heater core leak, the problem would exist at any setting, and probably get worse in defrost (at leat in the begining).

The manual says that the system is not in recirculate mode when in the defrost position, and the windows clear when in the defrost position. So, if it were incorrectly in recirculate mode in the AUTO position, the automatic defrost cycle would not work right. BUT, that would be an electronic problem, not a mechanical problem.

so! When you click to defrost you engage the A/C compressor which will have a tendancy to "dry" out the air! Does its smell "sweet" like antifreeze in the car? Either that or you have water puddled somewhere in the car!

I would suspect clogged pollen filter or wet carpets. Also check that the air exhaust in the rear are not blocked, if the air flow from any vent increases when you open a window this is probably the case...