mechohaulic Posted October 31, 2022 Share Posted October 31, 2022 don't want to cut out "mid-stream" on this topic ; not much choice any more . 10pm on east coast. take care of my lite work ok JOJO 😁 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/3/#findComment-514137 Share on other sites More sharing options...
usrjcro11 Posted October 31, 2022 Author Share Posted October 31, 2022 I will do some testing tomorrow. Thanks all for replies. Will report back 2 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/3/#findComment-514138 Share on other sites More sharing options...
Solution Hans Remmers Posted October 31, 2022 Solution Share Posted October 31, 2022 The toggle switch should get its air supply from a common dash manifold. At operating pressure (90 psi and above) you should hear a short exhaust of air when flipping the switch down, less than a second. The toggle switch supplies air to a pilot control valve located near the leveling valve. When air is supplied to the end port that the toggle connects to the suspension should exhaust out of the pilot valve exhaust port. This functions independant and after the fact of the leveling valve. The pilot valve is a round canister about 1.5" x 1.5" with a 4 bolt mounting flange. They are notorious for hanging up and plugging up, especially if it sat around. Make sure the exhaust port is clear and disconnect the lines and spray penetrating oil in the pilot valve ports. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/3/#findComment-514140 Share on other sites More sharing options...
Popular Post usrjcro11 Posted November 1, 2022 Author Popular Post Share Posted November 1, 2022 18 hours ago, Hans Remmers said: The toggle switch should get its air supply from a common dash manifold. At operating pressure (90 psi and above) you should hear a short exhaust of air when flipping the switch down, less than a second. The toggle switch supplies air to a pilot control valve located near the leveling valve. When air is supplied to the end port that the toggle connects to the suspension should exhaust out of the pilot valve exhaust port. This functions independant and after the fact of the leveling valve. The pilot valve is a round canister about 1.5" x 1.5" with a 4 bolt mounting flange. They are notorious for hanging up and plugging up, especially if it sat around. Make sure the exhaust port is clear and disconnect the lines and spray penetrating oil in the pilot valve ports. This was problem. Truck had been sitting up for about 6 months. Exhaust line was plugged. Took exhaust line off and it worked. Thanks all that contributed. Newbie in learning curve. 1 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/3/#findComment-514175 Share on other sites More sharing options...
Joey Mack Posted November 1, 2022 Share Posted November 1, 2022 thank you for posting the solution.... It will help someone else with the same issue... jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70636-1994-mack-ch-trailer-coupling-and-uncoupling-not-working/page/3/#findComment-514176 Share on other sites More sharing options...
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