On a couple recent long trips, after a couple of hours I find I have lost air flow through the vents to the extent that barely a breeze comes out even with the fan on full blast. The fan runs at all speeds, and the zone selector functions normally. A hissing noise can be heard from the dash, seems to come from the vents or the base of the windshield.

I found that in order to temporarily remedy this problem I can just shut the AC off. After about 10-30 seconds, the airflow returns to normal and I get a surge of very cold air, followed by non-conditioned flow through the vents. At least I can keep air coming in the car this way. I can then run the AC for 20 minutes or so at a time, or until I notice the flow diminishing, and then rinse-repeat.

Since I have had the car I sometimes notice a musty smell from the vents, especially when turning the AC on and off with the button while airflow and zone settings remain constant. I also have this mysterious white dust on the surfaces in the car, could be some kind of stuff coming out of the vents since I did not have it before this spring.

Anyone have this problem? What was the solution? How bad did the dash squeak after R&R!?

 

Sounds like your AC system is freezing up. Ice forms on the condensor and doesn't allow air to pass through it. When you turn off the AC, the compressor stops cooling the system, and the warm air thaws the ice, thereby allowing airflow to return. That's what happens, but it isn't right. Usually the cause it low freon in the system. have it checked by a repair center or dealer.

 

Try removing the cabin filter

 

The evaporator core is freezing up; the dash is coming out next week so they can replace the entire HVAC box.

 

This older tsb for a f-150 may explain the white powder.


http://www.ford-trucks.com/tsb/fullt...p?tsb=05-10-11

 

update:

The white flakes were flux from the a/c evaporator core. That has been changed as well as the enclosure, afaik.

Drove the car for 40 minutes after the repair, noticed I was getting cold (It's winter here, I had the selector on defrost/floor)... no airflow. Switched to dash only with the blend left on the warmer side.. 1 minute later full flow again! So the issue remains.

The tech has sent/is sending an email to Ford about this, I assume everything checks out as far as system pressure... maybe the a/c clutch is sticking "on", maybe there's some problem with an orifice somewhere, I don't know enough about AC to make a diagnosis.

The car came back spotless and flawless though, despite having the dashboard out and the intake manifold off to disconnect lines/undo bolts. I have to hand it to Ford and to my Tech. Real happy.

 

The second fix was a small pressure switch under the hood.

The white flakes are back, which is why I searched for them, and found only my thread.

Seems like I'm the only person with this problem!

I'll probably live with it. :\

 

Don't all cars have dandruff of some kind?