Do i need a new air dryer?

[tree98]

I have a 2005 Sterling lt7501 crane truck and lately something in the air brake system has been freezing up. Twice in the last 45 days the truck was stuck on the side of the road because it wouldn't make air. We had to take the output hose off the compressor and get alcohol into the system for it to thaw out and build air again. Seems to take about 20-30 minutes of highway speed driving when the temperature is in the teens or less for it to start acting up. I heard the dryer discharge so I know it's atleast doing that. I have other trucks out in this same weather and they aren't freezing up so it must be something with this truck.