dover Posted September 28, 2015 Share Posted September 28, 2015 Good evening everyone,Its been a while since i've been on the site. I have an early 70's hobbs 40' flatbed that I picked up for $600 over a year ago. It had 6 of the 8 tires in 50% or better condition so I figured why not. When I hooked it to the truck a while back and charged the tank the brakes would lock up. I figured it was a relay valve leaking internally to the service side. It is a single tank with no spring brakes. I was able to get it home by leaving the trailer circiut uncharged and hoping the friendly NHP trooper that stopped me for a flat spot on the trailer didn't decide to crawl under the trailer. It worked as I only got a ticket for the bad tire. I ran new lines from the front to the tank and bought a new valve. I put the new valve on last night and now it's not charging the tank when I put the air to it from the cab. When I pull the Johnson bar it charges the tank and locks the brakes. I have service hooked to service and emergency to emergency. What am I missing? I know its not in the truck because it works fine with the other two trailers.ThanksBen Quote 1962 B733 L cab Link to comment https://www.bigmacktrucks.com/topic/41977-air-brakes-locking-on-trailer/ Share on other sites More sharing options...
b61mack Posted September 28, 2015 Share Posted September 28, 2015 Switch the glad hands around, sounds like they are backwards. Quote Link to comment https://www.bigmacktrucks.com/topic/41977-air-brakes-locking-on-trailer/#findComment-305398 Share on other sites More sharing options...
m16ty Posted October 28, 2015 Share Posted October 28, 2015 Switch the glad hands around, sounds like they are backwards.This could be right. looking at the front of the trailer, the standard is red on right and blue on left but every once in a while you can find them swapped on old trailers.You could also have the same problem I experienced just the other day on a trailer. It had been sitting awhile and something had built a nest inside the service glad hand. Truck started rolling fine but when I hit the brakes, the trailer brakes locked and wouldn't release. The nest had allowed air to go to the brakes but wouldn't let the air release when I let off the brakes. Took the line off the transport valve back at the trailer axles, blew air through the line, and the nest came flying out. Quote Link to comment https://www.bigmacktrucks.com/topic/41977-air-brakes-locking-on-trailer/#findComment-309025 Share on other sites More sharing options...
carlotpilot Posted October 28, 2015 Share Posted October 28, 2015 provided you have everything hooked up right and did not replace the valve with the wrong one charge the air tank up the brakes will lock up pull the emg button out then push it back in your brakess will release and work as they should Quote Link to comment https://www.bigmacktrucks.com/topic/41977-air-brakes-locking-on-trailer/#findComment-309028 Share on other sites More sharing options...
farmer52 Posted October 28, 2015 Share Posted October 28, 2015 Install glad hand seals with screen inserts to prevent nests in the air lines. 1 Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/41977-air-brakes-locking-on-trailer/#findComment-309058 Share on other sites More sharing options...
Maddog13407 Posted October 29, 2015 Share Posted October 29, 2015 common problem with nests in the glad hands. have had that problem with the brakes not wanting to release. went to change the valve and found that when I charged the line with air, I pushed the nest right thru the line to the valve and plugged it up Quote Link to comment https://www.bigmacktrucks.com/topic/41977-air-brakes-locking-on-trailer/#findComment-309126 Share on other sites More sharing options...
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