How do you get air pressure to the air line that is in the propane compartment? Does the engine have to be running?
Yes engine needs to be running and air pressure up to pop off on dryer.
That line should be coming off one of the brake tanks. On mine it's the rear. If you have air in the tank it should work (until it empties) but if it has leaked out, you'll need to run the engine. On the older coaches like yours, your aux air compressor does not try to maintain pressure in the tanks so it will not feed that line.
Thanks