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1994 Mack CH trailer coupling and uncoupling not working


usrjcro11
Go to solution Solved by Hans Remmers,

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is the switch for fifth wheel slide?   What is it for, send a close up picture of the switch...  some of these trailer switches require the trolley handle to be applied..   jojo

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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.

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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

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the air switch takes air from the tank through a regulator in a pro set-up. then sends it to the leveling valve to the 'pilot' port..  the valve dumps the air for you, so you can hook or unhook. then flip the switch and suspension rises to a preset level..  

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since you located the leveling valve can also try disconnecting one end of the arm; usually the lower end . with ful air pressure and ALL body parts out of harms way,, just slightly move the arm up/ down. if there's air and valve is good the bags should  raise/ lower. 

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