Originally Posted by superdave
ok you have my attention. i have 2 tanks,do they all have 2? i have a air door, when i remove that door can i hook up my air chuck to the door control valve line? i noticed 2 needles in my air gauge, is that for the primary and secondary? thanks
All don't necessarily have two tanks, just two systems -- there may be more than two tanks. I haven't made a point of counting them, but from memory it seems like mine might have 5 tanks..? This might be because my bus has ABS brakes, and I can imagine an ABS stop is going to consume a large volume of air quickly so they'd install extra tanks as reserve for that.
I guess you could hook up to the door control valve line, but it's probably just 1/4" tube, which is going to limit the air flow (compared to connecting to a shorter and/or larger diameter point). It shouldn't be too hard to start at the compressor on the engine and follow the tube past the drier to the first tank. The tanks are often built with a number of bungs around them, and it might be that yours has an extra where you can simply remove the plug and connect your own stuff. If not, there's always the tee option.
Oh.. yes, the two needles in your air pressure gauge are usually green for the primary system and orange for the secondary. But don't ask me which systems do which part of the braking -- I don't know!