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You can check the 4 and 6 way plugs with a multimeter to see what’s going on other than left/right/brake and marker. I doubt A is brake air, it looks open in the picture instead of the usual female normally closed connector. No clue what B is.

[Dick]

Thanks

[DON]

Can you get a closer photo of the other connections – the 4 and 6 pin plugs are obvious but… the other ones are not clear enough (at least to me)

A spray looks like an air line…. just hard to be sure.

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A looks look like an air line hook up. I wonder if B could be a feed for a remote mounted camera for the stacker.

Craig.

[DON]

B pin DC power to feed trailer, 4 pin could be for trailer camera

[Jim]

I’m sure A was just accessory air, you would need two air hook ups for air brakes. You’d normally have two glad hand connections, one to release the parking brake and the other applies air pressure for the service brakes.

The 6-pin connector should have your electric trailer brake power. A 7-pin connector would also have reverse lights if you wanted to convert it.

[Greg]

You need two air connections for a big trailer with spring brakes… but if it was for a Towed with an M&G air brake system you’d only need the one. Actually, come to think of it, I’ve never seen a trailer brake handle in a Prevost… could be an option but I haven’t seen one

You could test it easy by hooking up an air hose with a air gun and test it. See if it puts out air just sitting there. If not, go further and have someone step on the brakes while you hold the air gun open and see if air comes out. If it Does then you could use it for a towed.

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Thanks for the info everyone.

It did have a camera set up for the trailer, and I discovered a 7 pin connection in the engine compartment.

I’ll test out the air line, as suggested, next time I get to the coach.

[Dennis & Jackie]

It’s unusual to see a Marathon with blue coloring from early 2000’s. What is your coach number

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I still can’t get past that air coupling, it appears to be an open fitting which can’t be hooked up for brake or acc air. Which is it?

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If I had to guess, I would think is was for an air ride system for a trailer and the 4 pin was for the air valves, raise, dump, two axle lift etc.. I had a set up like that as far as the 4 pin on a Featherlite trailer, however it had glad hands, maybe the trailer had electric brakes with air ride? I had switches in the truck to control the air for the trailer, it was kind of low, so it was nice to be able to raise it, save the tires on slow tight turns, stuff like that. So look around the drivers for some switches, or trace the wires??

[Roger]

As a cynic I would be very careful about identifying what is going on with the light, camera and air systems on your coach. I don’t believe it is necessary to get beneath the coach to see what is going on, but you do have to use a multi-tester to verify what pins are hot when the lights, brake lights and turn signals are on.

The air likely did not engage the trailer brakes, but could have been used for an Air Force One or M&G supplemental brake. If the coach has a brake controller near or under the dash that will be a good clue about if the trailer brakes were electric or air.

[Roger]

Lets see if can catch up with the questions.

Truk4u; It’s a female (closed) fitting

Racerdave; the only switch I can locate is for the camera system.

Jon; thanks for your concern, I hadn’t really meant to get under the coach. just poor word choice for testing the plugs. It does have a electric brake controller under the dash, but I was told that the coach MAY have also been set up to air brakes for the trailer.

I was hoping to use the M&G brake on my Toad.

I hope to get to spend some time with the coach next week and will update everyone as I make progress

[Dan]

Depps

thanks tor your number. 750 was first owned by “horse people. Then an owner “Greg” had the coach here in Coacgella Valley after buying it from consignment at Freedom RV in Tucson. Then a member of this forum bought it and towed a large stacker like trailer before relocating to Europe. So I suspect the large stacker car hauler had air brakes and suspension and maybe a rear camera. I forget all he had added. So you have a very unique bus, we’ve always liked it after seeing it in Jackson, Wy in 2003. Here list. (2001) 684, (2002)741, 750, (2003)784, 820, 826, 829, 830, 836, (2004)839. That’s it for 40 ft XLII’s built by Marathon. Being a 40,l and 500 hp, I bet you’ve noticed it’s a little hotrod

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Thanks