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air problem M931 tractor

M931

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i got this M931 will use it with semi trailer, problem is when i push trailer button it stay in, until i open valve to airhose to trailer, then trailer button pop out,cut off air.. need help.:shrugs:
 

Floridianson

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I do believe if it free flows it will shut it's self down. When you hooked it to the trailer did you hold it in till the trailer tank was full.
 
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Pahoa/ HI
Hook up the airlines to the trailer. Turn on the valves for the lines to the trailer. Get in cab and pull and hold trailer release button till it no longer pops back in.
 

Floridianson

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Is it a Military trailer. Do believe the valve on the dash is a trailer protection valve. If there is a no air in certan tank or a large air loss on the trailer the valve pops out to protect the truck. Seems like all the military trailers I have do not need air to release the parking brake because them don't have them. Did you hook up the emergency line (red one) and try and air up the holding tank on the trailer. The only outher thing I can think of is you PPV is not allowing the correct truck tank to fill.
If I rember the valve is pushed in to release the air from the truck to the trailer air service brakes as said not there to release the trailer parking brakes.
 
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M35A2-AZ

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The truck has a Tractor protection valve on the frame. Try to test the valve, leave the red hose stored on your truck and then push in the dash valve.
The dash valve should say in, if not the valve maybe bad. Or the TPV maybe bad or the air supply to the valves.
 

Floridianson

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The TM has us hold the tractor protection valve that in the cab in for 15 seconds to charge trailer reserve service tank. The way to check the in cab protection valve is to have everything correct on trailer hook up and trailer charged. With full air pressure showing in cab and all correct with air system then you would have the tractor protection valve pushed in as in normal driving with trailer. Then apply foot brake on and off till air pressure drops to a certian amount then the tractor protection valve in cab should pop out letting you know that the truck will no longer support trailer brakes. As said civi trucks have yellow and red valves on dash. Red supplys trailer air to release the parking brake. Military does not. We just have trailer protection/service and a what they call emergency air ports.
 
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M931

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you are right.. it is civilian trailer, with air ride suspension and need air to release brakes.. thats the problem.. on my truck there is air coupling to connect to trailer, and there is always full air pressure.. maybe use that to connect to semi trailer..
 

Floridianson

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That is why I wanted you just to try and connect the red line and charge the parking brake release on the trailer.
I'm still trying to figure out what TinyDragon is talking about because my valve in the truck (M931) is in the out pisition and when you need to use trailer you push in to charge the system and give control of the trailer brakes to the tractor.
 
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I meant, to say " push in, not pull out." I've moved many trailers with my m931 both civy, and military. I found that it is easy to get the lines mixed on the civy trailers. Especially on a well used trailer where the glad hands paint is gone or the air line tags are missing. Sometimes I'd have to swap the lines to get them to work right. Trailers with airbags may a long time to fill.
 

M931

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i have work on it today.. clean the trailer valve, and start up again, i have run engine about 1500 rpm. now it is working, yes it take some time before there is pressure on the semi trailer, have to push button for long time and it stay in.. i believe it works now.. thanks for help.. :driver::clinto:
 
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