fogging windows

99 malibu windows fog when it gets 30 or below. Good heater and air. Anyone know why this is happening?

Leaking heater core, dash has to come out to replace it. You will smell antifreeze with fan on. Cost around $700 to get it done. You can bypass the heater core by disconnecting the hose and reroute it back to the engine.

this would be true if the heater core was leaking . but this has been going on for over three years and thats why its driving me nuts...its ok above 30 but under 30 the windows fogg up and it not just 1 its all of them ......thanks

Then I would guess water leaking into the car, truck, taillights, windshield etc. Check under the carpets for moisture/dampness.

99 malibu windows fog when it gets 30 or below. Good heater and air. Anyone know why this is happening?


a leaking heater core or a plugged air box drain will do it.

do you add coolant ? if not then check that water drains out the air box.

if that is good then check all carpets/under carpet for wetness. the in trunk check for wetness.

windshields are big , sometimes the rear window will leak.

what you have is a high dewpoint caused by excessive mositure in/getting in the vehicle. when you heat up the interior this wetness start evaporating making the dewpoint to high so the condensation forms on the cold windows.

if you had a few woman breathing heavy that also would do it.

Check if your cabin air intake is stuck in recirc-- listen for door to move as you press inside and outside air--- foggy windows will always happen on recirc between 32 and 42 degrees.. no matter how much you have the defrost on-- that is why recirc is never on when in defrost mode