usrjcro11 Posted October 30, 2022 Share Posted October 30, 2022 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 Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/ Share on other sites More sharing options...
doubleclutchinweasel Posted November 2, 2022 Share Posted November 2, 2022 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. Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-514251 Share on other sites More sharing options...
67RModel Posted November 2, 2022 Share Posted November 2, 2022 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...... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-514252 Share on other sites More sharing options...
usrjcro11 Posted November 3, 2022 Author Share Posted November 3, 2022 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 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-514274 Share on other sites More sharing options...
mrsmackpaul Posted November 3, 2022 Share Posted November 3, 2022 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 Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-514288 Share on other sites More sharing options...
usrjcro11 Posted November 4, 2022 Author Share Posted November 4, 2022 I will be ordering new valve tomorrow. will update when I get it in and replaced. thanks 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-514335 Share on other sites More sharing options...
Solution usrjcro11 Posted February 27, 2023 Author Solution Share Posted February 27, 2023 Sorry for being late updating post. New valve corrected problem. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-526134 Share on other sites More sharing options...
mechohaulic Posted February 27, 2023 Share Posted February 27, 2023 good to hear problem corrected and just as important;; thanks for update. Quote Link to comment https://www.bigmacktrucks.com/topic/70637-1994-mack-ch-air-coming-out-of-red-line-to-trailer-but-trailer-air-button-not-engaged/#findComment-526136 Share on other sites More sharing options...
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