frozen brakes?

NO brakes. zero. How about on the truck. How much air pressure do you have. Primary and secondary. How cold is it where you are and how long have your brakes been set.

 

Set the trailer brakes and tug. Release trailer brakes and pull trolley and tug. May be just a problem with the trolley valve.

 

Does your foot pedal activate your trailer brakes. You would need someone to watch while your doing this. Not sure how else you could check that. Does your trailer brakes set when you pull the knob in dash. Are you sure the brakes are adjusted the right way. I had a driver that had over 15 years experience he was having brake problems. He said he adjusted trailer brakes with nothing helping. He took it to a shop and the mechanic told me the brakes were backed off all the way. Good luck.

 

First course of action is to narrow it down...find out where the problem is. Unhook the blue line and use the hand valve. Is air rushing out of the line? If not, step on the foot brake. If still no air, the problem is in the tractor. If air flows with the foot valve and not the hand valve, check the lines to/from the hand valve. If neither the hand valve nor the foot peddle causes air to flow out of the blue line, it is a tractor problem, and could very well be moisture collected in the blue line, settled in a low spot, and froze...a little airline antifreeze poured into the blue line and hold the end up so gravity gets the antifreeze to the blockage might clear things up. If air IS flowing from the disconnected blue line when brakes are applied with both the hand valve and the foot valve, it is a trailer problem, and airline antifreeze poured into the blue line, reconnect to the trailer, and pump the brakes to try to push it through the trailer air system.

With the problem being on the service brake side, it would be easy enough to pull the trailer into a shop to sit 30-45 minutes to thaw a bit and see if that clears it up before tearing into it too much. If thawing it out doesn't get the brakes working again, it could start getting expensive and time consuming as you trace the airlines to see how far the air is pressurized when the brakes are applied. SOMEWHERE there is a blocked line (hopefully ice) or stuck valve (hopefully frozen).

 

Sounds like ice in the brake lines or valves. If air is getting to the glad hands when the brakes are applied try this. Take the glad hands loose and pour in some rubbing alcohol then work the brake pedal for maybe 5 minutes to get the alcohol through the system. If no air pressure is at the glad hands when brakes are applied then look back up in the system on the tractor.

 

Sure you're not dyslexic and yanking on the turn signal lever?? (Sorry, couldn't resist)

You'll have to take a few simple steps to narrow it down by process of elimination.
Pedigreed Bulldog outlined it exactly as I'd start doing it. Had that occur twice and both times it was moisture froze in line (0-10° temp at time), but that's not saying it will be your problem specifically.
I might add... if you have a helper, have him/her look at movement of the brake chamber rod(s) while #1) Pushing on the brake pedal (popout valves released, naturally) compared to #2) Pulling on the trolley valve. It's just a quickie test, provided you have a helper. Brakerod stroke on the rears "should be" relatively the same, for both pedal or trolley.

 

Maybe I'm naïve but if I have a toothache I go to a dentist and if I need a jetplane ride I go to an airport. If I need a mechanic I don't go to a truck driver. A dollar saved to a career lost?