Excellent point Richard. While it is likely that the brakes may still be up after a week, you would be fortunate indeed if your Supply tank hadn't lost enough air to get a low pressure light. You may not have as many air connections as the 1990+ models do but a coach that holds Supply pressure for over a week is a good tight system. Mine certainly won't.
There should be two gauges for air pressure, Brakes (which has 2 needles - one for the front tank pressure and one for the rear tank pressure) and Supply (which has a single needle). I just checked and I get a low air pressure light if the pressure in the Supply tank is below 65 psi even if the pressure in the two brake tanks is well above 65 psi. You should get a low pressure light if the pressure in EITHER of the brake tanks drops below 60-65 psi but that would be hard to verify because a leak from either brake tank should immediately be refilling from the Supply tank so the Supply tank pressure would be dropping immediately to equalize the pressure between it and the lowest pressure brake tank. There are check valves in each of the brake tanks to prevent them from bleeding back into the Supply tank.
|