Intermittent A/C Problem in 2015 Passat

When driving on the interstate for about 15 to 20 minutes, the A/C stops coming out of my vents (no air at all). Turning on the re-circulation doesn’t do anything. It sounds like the blower is on, just no air comes out. This does not change when turning to floor vents or defrost. Never any problem with the A/C when driving in town, even for extended periods (for example, I was driving in heavy traffic for about 45 minutes today), or car in park with the engine running. I have the climatic, not the climatronic A/C system. Shops can’t diagnose because air starts blowing by the time they get the car back to the shop. Any ideas what it could be?

If you’re allowing outside air to enter the vehicle with the AC on, and it’s humid enough, it can frost up the evaporator, reducing air flow.

Always set the vent system to re-circ when operating the AC.


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The evaporator coil is icing. The next time the air flow stops while driving on the highway, switch off the A/C compressor but leave the blower on, the air flow should be restored in 5 minutes.

This is caused by a malfunction in the systems pressure control, if the low side pressure drops below 30 PSI the temperature of the evaporator can be lower than 32 degrees and icing can occur.

The repair depends on the way the A/C pressure is controlled on this vehicle, there is a thermistor in the evaporator to monitor the temperature that can fail. Some cycle the compressor to keep the pressure from dropping too low, others have a variable displacement compressor that will adjust upon demand.


Everyone that I know that has that problem is a smoker, and has a window rolled down a little bit.

Is the evaporator coil icing something that could be confirmed visually? (I don’t know much about car problems, unfortunately).

So, the heat doesn’t work either in these situations, so I’m not sure it is an evaporator coil icing.

All of the air for the heater first passes through the evaporator coil, if the evaporator is blocked, there will be no air flow for the heater.

I see. But would the evaporator coil still ice in that situation?