tractor/trailer airbrake problems..

[jdknech]

well, i went friday morning with the M932A1 to pick up my new(to me) xm971 semi trailer.. when i hooked up, i found a blockage on the trailer "service" side, but the big problem was that when i pushed the "charge trailer air" knob in the cab of the truck, i got a slight hissing sound under the dash, and only 10-15psi at the emergincy gladhand... and when i removed my hand from the knob, it just popped right back out, and would not stay in the "charged" position...
the emergincy gladhand at the end of the frame by the pentle hitch is working fine..
is this a common problem? is there a simple fix?

thanks for the help guys- Josh

 

[73m819]

Have to have the "tractor" valve in FRST or together

 

[rosco]

Offhand, sounds like faulty Tractor Protection Valve, on the tractor. What was the "blockage" you spoke of on trailer? What kind of brakes on the trailer - are they full air? Were the trailer brakes ever on?

Did you have the Service side hooked to same/Emergency hooked to Emergency? That too, will give you those kinds of results.

 

[GHall]

Hold the knob in for 10-15 seconds... Maybe a little longer.

 

[jdknech]

Have to have the "tractor" valve in FRST or together

not sure i follow what your saying?

 

[jdknech]

Offhand, sounds like faulty Tractor Protection Valve, on the tractor. What was the "blockage" you spoke of on trailer? What kind of brakes on the trailer - are they full air? Were the trailer brakes ever on?

Did you have the Service side hooked to same/Emergency hooked to Emergency? That too, will give you those kinds of results.

the trailer is air over hydraulic brakes, and the blockage was "grass" or something in the lines... but i never did get the trailer brakes to come on.. the service side was still blocked, and i couldnt figure out how... as far as the trailer, i will just run new lines.. and the gladhands were hooked up right.. thats the first thing i checked..

 

[jdknech]

Hold the knob in for 10-15 seconds... Maybe a little longer.

i tried holding it a couple of min.. and got nothing.. i then disconnected the gladhand, and had my brother check to see if any air was coming out when i pushed it in, and he said it was barely any.. maybe 10psi, not nearly as much as it should have been..

 

[RAYZER]

The debris in the trailer air line may cause problems in the trailer air system.
may need to be taken apart and cleaned!

 

[jdknech]

The debris in the trailer air line may cause problems in the trailer air system.
may need to be taken apart and cleaned!

they will need cleaned, and that is on the list to do before i hook the truck back up to it.. but i was also trying to figure out why I'm not getting any pressure to the emergency gladhand when i push the "charge trailer air" knob on the tractor dash..

side note, i really like your camper conversion! i hope mine is half as good!

 

[Artisan]

Start on page 432 of the -10 Manual.

What happens when you do a COLA test?

 

[wreckerman893]

On a straight air brake system when there is no air on the trailer the brakes will stay locked until enough air is put in the system to release them.
On a air over hydraulic system the brakes will not lock up when there is no air in the system (we always double chocked the older trailers if they were parked on an incline). That is why you have to back up close enough to the trailer to hook up the air lines, pull the trailer brake lever down to put air on the system to keep the trailer from rolling backward while you are coupling to it.
On some straight air brake tractors it is necessary to hold the charge valve in for a while so the whole system can charge. If the air tanks in the trailer are empty it may take a while.
Did you check all of the air bags to make sure you weren't losing air from some other place that the brake lines?

 

[jdknech]

I never got enough air through the emergency line to air up the bags... once I got it home, I hooked up a compressor to the emergency side of the trailer, and it held air just fine, and hasn't leaked down over the past couple days.. so I would say that part is good.. I'm starting to think I might have a bad "tractor protection valve"?

 

[wreckerman893]

[QUOTE.. I'm starting to think I might have a bad "tractor protection valve"?][/QUOTE]

That's a possibility.


When you push in the Valve does it sound like a full charge of air is coming out of the hose?

You do know you have to push in both the SERVICE and EMERGENCY valves to charge the system correctly right?

Are you sure you hooked up the hoses correctly? Someone may have mislabeled them.

I used to have some troubleshooting tricks but I'm having an attack of CRS right now.

 

[jdknech]

i did not know i was supposed to charge both lines at once.. are you supposed to do this by pulling the "johnny bar" and pushing the charge air knob at the same time?
and no, when I push the valve in, it does not sound like a full charge of air..

I am 100% sure the lines were hooked up right, I traced them all the way back the the axles..

 

[quickfarms]

the emergincy gladhand at the end of the frame by the pentle hitch is working fine..
is this a common problem? is there a simple fix?

thanks for the help guys- Josh

On my tractor, it is not a M931/2, I have glad hands on the front bumper pintle hook, pogo stick and rear pintle hook. All three are plumbed to the tractor protection valve and each glad hand has a shut off valve. Since you are saying the pintle hook works but the pogo stick does not I look for a shut off valve that needs to be open or a selector valve

 

[jdknech]

the shut off valve is right where the pogo stick is, and i made sure it was on, but I'm pretty sure that the rear emergency gladhand is NOT run through the protection valve.. i use it all the time as a air line hook up for airtools.. and have never had a problem, or had to push in the charge trailer knob on the dash.. or, who knows.. maybe it's supposed to be plumbed through it, and my system is just really screwed up..