This just happened to my friend on a 2008 Allegro Bus. Unscrew the center dash cover (instrument panel) holding the speedo, tach , air pressure gauges. On the back of the instrument panel you will see a red & green airline. These airlines are pushed into metal fittings that are screwed into the back of the front & rear air pressure gauges. On my friends coach we only saw a green line as the fitting holding on the red line had self destructed. This caused the red line to act like a high pressure water hose flailing around inside the dash lodging in a far hard to reach corner. You can find it by following the air flow. You will need to purchase a new fitting that screws into the back of the air gauge, then push the hose into the fitting so it will lock. The old fitting will not be reusable.
