Jump to content

1994 Mack CH air coming out of red line to trailer but trailer air button not engaged


usrjcro11
Go to solution Solved by usrjcro11,

Recommended Posts

Unhooked from lowboy trailer today. Discovered air coming out redline when I press brakes without trailer air supply engaged. When  I engage trailer air supply air comes out of blue line for trailer which I understand. Is air supposed to come out of the redline with trailer air supply off? If not what do I need to check?  Thanks

Link to comment
Share on other sites

Sounds backward.  Red line (IIRC) should pressurize when trailer air system is charged.  Blue line should be "service" brakes, pressurized when service brakes are applied (foot valve or hand valve).

I'm sure the brain trust will chime in here before long.

"Eagles may soar, but weasels don't get sucked into jet engines."

Link to comment
Share on other sites

Yes I would go back and make sure what you are saying is actually happening because its very backwards. When you press in your red button on the dash a flow of air will pass through the red emergency line hooked to the trailer and release the spring brakes on the trailer as well as fill any onboard air tanks the trailer may have. Once the red button is pressed on the dash air should only pass through the blue hose when the foot valve is depressed or the trailer brake valve (trolley valve) is used. If what you say is in fact happening then I guess the two places to look would be the air supply valve (red and yellow buttons) or perhaps the tractor protection valve. I cant understand how that would be happening unless somebody put a new set of hoses on the truck and switched them but then if you had them hooked up to the same color glad hands on the trailer the spring brakes on the trailer would have never released.....Something ain't right here......

  • Like 1
Link to comment
Share on other sites

Well you both are correct. Lines are backwards. I was just hooking to old lowboy trailer whichever way made brakes release. No color codes on trailer.Am I correct by saying no air should come out of either hose without trailer service valve pushed in? If this is correct then is trailer protection my problem with air coming out of trailer line without trailer service valve pushed in?

thanks

  • Like 1
Link to comment
Share on other sites

10 hours ago, usrjcro11 said:

Well you both are correct. Lines are backwards. I was just hooking to old lowboy trailer whichever way made brakes release. No color codes on trailer.Am I correct by saying no air should come out of either hose without trailer service valve pushed in? If this is correct then is trailer protection my problem with air coming out of trailer line without trailer service valve pushed in ?

thanks

Well yes and yes

Yes you should have no air coming coming out at all when the trailer supply valve isnt pushed

Amd yes the tractor protection valve isnt working 

 

Or at least thats what I undersunderstand is happening 

 

Paul 

Link to comment
Share on other sites

  • 3 months later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...