usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 When I flipped switch another person was by fifth wheel and did not hear any air discharging nor saw airbags go down. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514106 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 forgot when moving the arm make sure it's still connected to the valve NOT the rear end. might sound like "i'm not that stupid". not implying anyone is ; after 50 yrs of road calls it's the question that sound "stupid "make a difference when not being there to physically check an issue. a quick one;; call in liftgate doesn't work :: reply is the power cord plug in the trailer ? response ;; yes it is ;; OK 1 1/2 later arrive to find power cord UNPLUGGED back of tractor.. driver==you didn't ask about the other end!! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514107 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 Mechohaulic fully understand. Need all help I can get Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514108 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 possibly bags are down now, depends on the style bag. some have only a short travel Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514109 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 I will take pictures tomorrow up and down. Noticeable difference. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514111 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 i would go back to disconnecting leveling valve arm from rear end and physically moving the arm ;; air movement will be heard /bags will change. if not do as JOJO stated remove the supply line to the valve. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514112 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 1 minute ago, usrjcro11 said: I will take pictures tomorrow up and down. Noticeable difference. how is there a difference? have the bags inflated/ deflated ? if so I don't under stand the situation. unless you put an outside air supply to valve Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514114 Share on other sites More sharing options...
Joey Mack Posted October 31, 2022 Share Posted October 31, 2022 mech, with respect to him. He did say he was new at this.. its all good Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514115 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 Will test tomorrow. Where should the air exhaust from if switch is working properly? Leveling control valve? Behind dash? Wondering if I may have a plugged exhaust line. Dirt Dobbers are bad here plugging lines. Had a international truck with vacuum assist brake. Brake pedal hard but no brakes.put new booster on no better. Found exhaust line plugged from dirt dobber. Learn expensive lesson. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514117 Share on other sites More sharing options...
Joey Mack Posted October 31, 2022 Share Posted October 31, 2022 there is an exh. port on the leveling valve 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514118 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 total respect IS ALWAYS given. difference today is :: way way back when i said "i do"i consider myself "a doctor" .based on the fact : I had patience then . patients are gone NOW Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514119 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 Yes I can tell when bags are inflated after air builds up. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514120 Share on other sites More sharing options...
Joey Mack Posted October 31, 2022 Share Posted October 31, 2022 I have also seen the filter screen inside the air input port on the leveling valve, blocked up with red dirt... I guess southern red dirt can travel throught the smallest places... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514122 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 am I correct then the only situation when flipping the toggle was ; you weren't sure what the valve did ?possibly there is nothing wrong with the system . the bags work properly ? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514123 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 not understanding how a noticeable difference can be seen in the bags . they raise/lower. valve must be working Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514126 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 40 minutes ago, Joey Mack said: ok.... there is a leveling valve on the front drive axle.. make sure there is a supply of air to it. if not, let us know.. you can un hook the supply line after you reduce air pressure below 85 psi, then crank the truck and after 85-90 there should be air coming out of the line you un-hooked.. if not... the regulator at the tank is probably junk... also, remove the dash panel and see if the switch is an air switch or all electric.. post the results. jojo The air bags do not start raising till about 90 psi. Same time as air bag on cab starts raising. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514127 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 normal ;; correct JOJO at 90 the secondary air will be filling ?? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514128 Share on other sites More sharing options...
Joey Mack Posted October 31, 2022 Share Posted October 31, 2022 well that is correct... they will not rise until tractor protection valve opens up to supply air to the other systems..... only the brakes get the air above 25 PSI... It is a safety feature in big trucks... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514129 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 3 minutes ago, mechohaulic said: am I correct then the only situation when flipping the toggle was ; you weren't sure what the valve did ?possibly there is nothing wrong with the system . the bags work properly ? I knew what it was suppose to do but my air bags never purged air to assist uncoupling from trailer. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514130 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 what you are saying is now when pulling out the red trailer button, the tractor air bags deflate automatically/ Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514131 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 53 minutes ago, mechohaulic said: going back and forth on your other post about the air lines to trailer. a "94 is too new for me to know its air schematic. red button out shouldn't be air coming out trailer emergency line (red) during brake application. between that issue and air bags doing nothing with the switch ;first thought is someone has lines crossed. Sorry to confuse. Two separate issues. Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514132 Share on other sites More sharing options...
Joey Mack Posted October 31, 2022 Share Posted October 31, 2022 the red button is not part of this issue Mech.. It is a seperate switch, that only controls the rear air bags.. its actually a simple system, especialy on a 90's truck... 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514133 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 5 minutes ago, mechohaulic said: what you are saying is now when pulling out the red trailer button, the tractor air bags deflate automatically/ Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514134 Share on other sites More sharing options...
mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 trying to cross reference the two topics he wrote earlier dealing with same truck . earlier stated with trailer emer button out , air comes out the red hose when stepping on tractor brake pedal. now the suspension issue seems A OK , working on the air / emerg line 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514135 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 4 minutes ago, Joey Mack said: the red button is not part of this issue Mech.. It is a seperate switch, that only controls the rear air bags.. its actually a simple system, especialy on a 90's truck... Correct Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/2/#findComment-514136 Share on other sites More sharing options...
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