Air Systems : Name That Part

[RHOMBUS]

I am new to air brakes and air anything. Some things seem obvious, like electric air solenoids that trigger the face slapper. Other things, not so much. I'll post some pictures with descriptions.

Bus: 2002 Thomas HDX, Cat 3126B, Allison MD3060, Bendix ABS
Location: Between driver's seat and driver's wall
What is #2?

1 - Accessory air feed
2 - UNKNOWN?
3 - Electric air solenoid
4 - GND
5 - Signal wire for "DOOR OPEN - STOP"
6 - Air line to "face slapper" (flashing stop sign)

[RHOMBUS]

Bus: 2002 Thomas HDX, Cat 3126B, Allison MD3060, Bendix ABS
Location: Underneath front end of bus, between frame rails, on back side of first crossmember
What is #1?

1 - UNKNOWN?
2 - Signal wire from ?
3 - Air line to #1 in next picture (brake pedal valves)
4 - Wires to nowhere

[Scooternj]

Originally Posted by RHOMBUS

I am new to air brakes and air anything. Some things seem obvious, like electric air solenoids that trigger the face slapper. Other things, not so much. I'll post some pictures with descriptions.

Bus: 2002 Thomas HDX, Cat 3126B, Allison MD3060, Bendix ABS
Location: Between driver's seat and driver's wall
What is #2?

2 - UNKNOWN?

2 looks like a air regulator like you'd see on a compressor

Originally Posted by RHOMBUS

What is #1?

1 - UNKNOWN?
[/IMG]

Looks like an air fitting, but I could be wrong, and am basing it on what FMTVs (M109x-series trucks) and M-35 and M-939 series trucks have at the front and back for towing

[RHOMBUS]

Thanks, scooternj. So that air regulator is necessary so the air system doesn't blow the sign off the side of the bus?

[Scooternj]

Originally Posted by RHOMBUS

Thanks, scooternj. So that air regulator is necessary so the air system doesn't blow the sign off the side of the bus?

It allows the mechanic to tweak the pressure going to the sign. My face slapper was electro-mechanical, but I have a regulator over my doors will get removed and the line capped.

[cowlitzcoach]

I second the idea that #2 is a pressure regulator to keep air operated mechanisms from having too much line pressure or not enough line pressure.

As to what #1 is, I would have to have more context to know for sure.

#1 could possibly be the brake light switch although I wouldn't bet $$$ on it.

What is #1 attached to on the other side of the crossmember?

[RHOMBUS]

Cowlitzcoach, I was also thinking it could be a brake light switch, since the lights didn't come on until there was actual air pressure flowing. Nothing is on the other side. That one air line goes through and to the brake pedal air cylinder system... or whatever that piece is called. As for the wire, it disappears into a harness. I haven't traced it yet. I'm wondering what all of those other wires there are for as well. I guess my wire harness antics aren't done yet.

[mjh2901]

I'll throw in one other option. Pressure regulator is a good call. I have also seen air dryers / filters that look the same. Keep moisture from the compressor out of the solenoid and the actual door mechanics... Or the opposite and inline oiler.

[Booyah45828]

Originally Posted by RHOMBUS

Thanks, scooternj. So that air regulator is necessary so the air system doesn't blow the sign off the side of the bus?

You're correct. That is an air regulator. The little diaphragm they have to open the sign needs very little psi to open, vs the 120 psi provided by the bus air system.

As for the other thing, I'm not sure. It looks like it grounds something out seeing as how it is only one wire. I don't think it'd be for the lights because those two switches are in your third picture.

[rvingoffgrid]

the single wire switch is most likely A ground for low air pressure will activate a buzzer or light the best way to figure out what its doing is to follow the air line. the regulator is adjustable so the #2 in your first picture is the adjustment knob to increase and decrease pressure most of the regulator screw it in to increase out to decrease but there are some that are back wards. your stop sign (face slapper) sometimes use a pressure switch to turn on the flashing lights on them so the ground from the pressure switch may turn on the lights when air pressure is present.

[rvingoffgrid]

also the color of the line will be a tattle tall on most all buses the green is the primary tank, red is secondary and yellow is normally service as in anything not brake related that runs on air. so sense the line coming to the switch is red it would lead me to believe that its brake related as in low air warning most times a brake light switch is mounted closer to or on the brake treadle valve. and in most cases it has two wires as the ones in the brake treadle picture. on some newer buses they have a accelerator interlock for the wheel chair lift and when the doors are open but this is normally all done thru the engine computer via a electrical signal from the door switches.