I need HELP with my 99 FRUEHAUF TL XX

The mechanics are right--there are a couple of types of air suspensions that are set up(ie:wired) to dump when the parking brake is activated--I personally do not like them--but then again I do not swap trailers--I have mostly seen them on large fleet trailers--and I always figured it was to insure the air was dumped when trailer was dropped.
Having said all this--(although I have never personally been underneath to look!) most remote air dumps(in cab etc) are electronically controlled(versus--dump valve on trailer itself) therefore it seems to me, a qualified mechanic who understands how that particular system is wired to the trailer brake--should be able to re-wire your system so it does not dump when the brakes are applied. But I would strongly advise you to find someone highly qualified and trustworthy!
As for loading and unloading--there really is no need to lock your trailer brakes--as long as you are hooked up--frankly if you spend a lot of time in cold temps in winter months--you'll find it a pretty good practice not to.
Just my $.02

 

Wheel Chocks? would that hold it

 

The trailer is operating as designed. Some trailers have small legs that drop down between the axle and frame when the air is dumped, some don't. You can probably have the dump valve bypassed to eliminate this.

 

There's nothing wrong with the trailer. Someone either ordered it with the auto dump valve or added it later. It's designed so if a trailer is dropped loaded, the suspension won't deflate and cause the trailer to walk forward and put pressure on the dollys. It's either the leveling valve itself, or a pilot valve. If it's the leveling valve you just need to replace it with one without a dump (~$50), or remove the pilot valve if it has one.

 

i dont see how the dumping of the suspension with the activation of the trailer parking brake will be controlled electrically.. there's nothing electrical about the parking brakes. they dont illuminate any lights or anything it's all pneumatic, so if anything, it has to do with a valve or valves on your suspension like Jfaulk99 said.

should be a pretty easy find.. just have some one activate the trailer parking brake while you're under there and find the dump valve and start tracing air lines.. my dump valve was hidden in the "C" channel of a cross member and after two weeks of looking i finally got my wife to flip the switch in the cab while i was underneath and found it.