no air from service line

[Deuce007]

Hooked my m105a2 up to the m35a3 yesterday for the first time and It didn't take me very long to notice that every now and then the brakes will lock up. I had already started the trip so I just turned the valve for the service and the valve for the emergency air off. about 5 minutes later the brakes locked up again so I got out and opened the emergency/service valve and closed it again to build air to release the brakes. when I finally got home I disconnected the air line completely and opened the emergency valve and air came out but when I opened the service valve no air came out of it in either valve position would this be why the brakes locked up? If so does anyone have an idea why?

The other theory is that whenever I turn the steering wheel the low air buzzer turns on and the psi gauge jumps around for some reason so I am also wondering if this that telling the trailer that the tanks are low so it locks up because it thinks it is out of air. I have already tried to purge the tanks and a very small amount of water came out and I also tried tapping the manifold and that also didn't do anything.

 

[212sparky]

When you step on the brakes you should get air out of the service brake line. The emergency air releases the brakes, that way if it brakes free or hose brakes it stops the trailer.

 

[Deuce007]

When you step on the brakes you should get air out of the service brake line. The emergency air releases the brakes, that way if it brakes free or hose brakes it stops the trailer.

So the only time that there should be air coming from the service line is when the brakes are pressed?

 

[frank8003]

maybe

maybe
from a newbie

lube the powerpacks
lots of interconnections
it all went unused for a couple of whiles?

they might be 'stickin"
or maybe jusrt one be stickin
"backpressure"


or this is useless

 

[212sparky]

Yep, the service line sends air pressure to the relay valve telling the brakes to apply.

 

[steelandcanvas]

maybe
from a newbie

lube the powerpacks
lots of interconnections
it all went unused for a couple of whiles?

they might be 'stickin"
or maybe jusrt one be stickin
"backpressure"


or this is useless

Huh?


Deuce007: Have you downloaded the TM's for your truck?

 

[Deuce007]

yeah I use TNJ murray.

 

[steelandcanvas]

That's good. They can provide you with good answers.

 

[Rustygears]

If you get low air buzzer when turning the steering wheel, check for a big airleak in the air assist system. It's very, very common and comes from a few sources. The quick way to confirm is to close the little shutoff valve inside the engine compartment at the firewall on the driver's side. It's a small shiny brass needle valve. That will close off the air supply to the air assist system and isolate it. Then see if the lock-up problem persists. The emergency air supply is straight from the tank at system (gauge) pressure. The service air only flows when the pedal is pressed.

If you get trailer lock-up, it is likely due to a drop in the emergency air pressure (matching the reported drop in supply air pressure gauge). You must have a pretty severe leak. The compressor can't keep up. It's pretty low capacity to start with.

 

[nk14zp]

Did you have the hoses hooked up right?