more on the air bag system
In 79 and 81 Airstream used a different system for the airbags than on the later models. Each Airbag has two valves, one mechanical (leveling) and one electrical solenoid valve (to close the air line with ignition off).
The great advantage of this early system is the ability to level from side to side, as well as up and down.
If Sam has this system on his 81, it would also suggest that the solenoid valves are bad, leaking or disconnected, due to loss of pressure with ignition off.
Properly working solenoid valves also allow you to dismantle the pressure lines all the way up to the solenoid valves and never loose pressure in the airbags.
On this system, the small inline check valve only comes into play when the ignition is on (open solenoid valves) to prevent back leaking into the compressor.
1983 310 Classic Motorhome
1997 30' Excella Trailer