03 passat - weak defrost- looking for solution

Does the air conditioner work? That's supposed to come on is defrost mode; the dehumidified air greatly aids the defrost process. Also, how's the volume of air through the defrost vents? The flap that diverts the air may not be moving properly. Finally, you should not have the "recirculate" button pressed - that cuts the efficiency of the defrost process quite a bit. Note that on my car, there are visible results in "defrost" in less than a minute.

AC works great. Didn't know it had to be on with defrost.

Is this first thing after starting cold? You won't get results until the coolant has heated up. If your "heat" works great, then it's not the heater core. I'm in the camp that you may have a flap position issue with low air flow at the center vent.

Although a/c does aid in defogging the inside, it generally makes no difference in defrosting the outside of a window. Even without a/c it doesn't do too bad in defogging. My B5 has no a/c yet.

Scotts13, in defrost (windshield) position, it will not let you select recirc, fyi.

Defrost flap issue?

Was that meant to be an "I don't understand"?

Yes, if manual controls, they are connected to cables that operated the directional flaps inside the dash to direct air to different zones. If it not fully closing off in one zone, it can cause decreased air flow to the desired zone.

If auto controls, there may be a servo motor not working correctly.

Interesting... Just watched a video on YouTube. So now I understand what you are saying. How do I make sure this is the issue without pulling the glovebox out

How long does it take your heater to get warm? I think my is slow.

my 04 1.8T if left out in the cold (she's a garage queen) will start feeling warmth in the vents after about 3-5 minutes of driving.

VAGguy said:

Scotts13, in defrost (windshield) position, it will not let you select recirc, fyi.

Click to expand...

Hmm, my 2000 would. Do you know if that was design, or was the old girl broken?

Mine takes at least 5minutes to get going

Do you have manual controls? Can you feel resistance as you turn the knob to defrost? On my 2002 gls, the defrost flap is not rotating since the cable that connects the knob to it has become disconnected at the flap. All the air is directed down to the floor. You can get to the defrost flap from the driver's side above the gas pedal. I can rotate the flap by hand, although it's not that easy. I think there's a small panel to remove. I pretty much just set mine to mid-position, so the defrost is not that strong but still works.

scotts13 said:

Hmm, my 2000 would. Do you know if that was design, or was the old girl broken?

Click to expand...

Maybe broken? All three of my cars in my sig have the recirc locked out on windshield position.


In fact on my passats, if I had it on recirc and then turned the knob to defrost position, you could hear the recirc button click off.

I have a glx with climatronic

Trout said:

I have a glx with climatronic

Click to expand...

The odds of a flapper servo motor being the problem just got better.

The time and expense to fix it went up, too.

ran the climatronic self diagnostic test and the resulting error codes came back- 25b,4f7,4f8,4fa.

Recirculator flap motor 4fa
temp flap motor 4f7
footwell defrost flap servo 25B
central flap servo motor 4f8


My defrost blows air, it just not very hot and it takes awhile for it to work.

All of those codes are indicative of your description.

VAGguy said:

All of those codes are indicative of your description.

Click to expand...

Where would you start? Do I need to replace all of those flap motors? Should I have the coolant flushed first?

You'll never hear me recommend against flushing any fluid, but (since you say you have good heat) it's not the place to start here. Somehow, I don't see four flap servos all failing, either. Don't know much about Climatronic, but that seems more like a wiring or control module issue.