Can someone please help me with my trailer air brake problem???

Okay thanks. I'll. Heck those out and let you know what happened

 

Something wierd I was helping a buddy today driving an 01 Mack rd triaxle and I put the trolley brake on and unhooked the blue gladhand and no air was coming out? But it works perfectly with his trailer. How could that be?

 

Tractor protection valve. It blocks off air flow to the service gladhand unless there is system air pressure in the supply line.

 

If you have access to another truck and trailer swap around to find your problem, but like AModelCat said your blue hose should not be pressurized when you break it loose.

 

Okay thanks guys. I'm going to bring the trailer to my buddy's Saturday morning and hook the trailer to his truck. If the trailer works fine think my best bet is o change the valve in the truck?

 

Recheck hose connections first, could have one crossed during cab changeout