M813a1 air supply questions

[H500D]

Hello all, i have a m813a1 81 model, can anyone out there explain the four air lines that glad-hands connect to? I understand the 2 at the the rear are for trailer brakes. The front two, one says emergency with a on off valve the other says service no valve how are these to be used? One more thing on my truck i only have air to the passenger rear side. Thanks in advance for any help.

 

[Derrickl112]

the front glad hands are used when the truck is being towed to activate the brakes.

the other rear glad hand...i think air only comes out when the brake pedal is pushed.

 

[EMD567]

On the front, those gladhands are for towing. They have one way check valves to prevent air from coming out. They should be painted the same as the ones on the rear. The glad hands on the rear are marked EMERGENCY and the other SERVICE. Emergency should be painted red, and has full system air pressure all the time. Service is your brake circuit for anything that you might tow. It is painted yellow or blue(blue is the correct color) and will only have the pressure that the treadle valve(brake pedal) sends to it.

 

[fasttruck]

Reference EMD 567s post: when towing a trailer on the pintle hook it is also necessary to open the shut off valves on both sides of the truck to operate the brakes and close both valves when the traiiler is uncoupled. Valvesd are open when valve handle is across the line and closed when the valve handle is parallel to the line; the opposite of what you would expect. Dummy couplers hanging on chains are provided to keep insects etc out of the lines when the brakes are not in use.

 

[H500D]

HI every body thank you all for your reply's it clears up a lot of questions for me. but i am still a little confused, my truck in the front not rear says emergency it has a shut off valve and then other drivers front says service. when the truck is running their is no air in the front may be my truck is labeled wrong on the front but that still does not answer the question as to why there is a in line shut valve off on this glad hand. thanks again for every ones help.

 

[KsM715]

When your truck is being towed, (think of your truck as now being a trailer) you hook up the air lines from the towing vehicle to the front of your truck. Emergency glad hand enables the towing vehicle to fill the air tanks on your (towed) truck and the service gladhand operates the brakes on your (towed) truck from the towing vehicle.

 

[H500D]

thank you every body! seems i am a little slow but thanks to every one i got, once again thank you all!!!!