Hello!

I'm experiencing the following with my car and not quite sure what the problem is, so I'm asking here.

Recently, I've noticed when I turn on my front defroster, the entire windshield becomes completely fogged up and it takes a good 2/3 minutes to finally get it cleared. I found that if I run the AC the windshield doesn't fog up at all. This seems to happen most often when it's pouring raining and as you can imagine, that's when you really need a clear windshield.

The heat works fine and there's no signs of any coolant leaks or smell, so I'm somewhat puzzled. I'm not losing any coolant so I'm hesitant to think it's the heater core. I've read some threads about the interior cabin microfilters may be the cause of the fogging. My car is a '99 323i with 56000 miles.

Has anyone out there experienced this problem and does anyone have any suggestions of things to check. I have a service appointment in September and it's on the list of things to check. I just don't want the dealer to come back and say it's something that it's not and charge me a fortune if all it needs if microfilters..

Thanks in advance for any suggestions!
Bip

That's normal and happens a lot in the rainy, humid summertime weather. Usually, the system doesn't have a chance to really dry out completely, so there's almost always some residual condensation, water, humidity, etc. I pretty much am forced to use a combination of the quick-defrost plus A/C if I want to get it cleared quickly. After that, A/C alone does the trick. There's not much you can do about it. My microfilter was just replaced a month ago, by the way.

Many of the new cars automatically turn on the AC when you turn on the defrost because of this. A dirty microfilter can also contribute, or possibly a small heater core leak, which are often hard to detect.