By George Bliss
From several years of observations at campgrounds, it seems most RVers don’t know the importance of hooking up the umbilical cord from the truck to the fifth wheel trailer before trying to connect (or disconnect) the king pin to (or from) the fifth wheel.
This is necessary so you can apply the brakes on the trailer, and is a “must-do” to avoid pushing your trailer off its leveling blocks or to prevent it from moving even a few inches – which would put great strain on the landing gear. If the trailer rolls or you don’t get a good king pin connection, your trailer can be sitting on the box rails of your truck – a very expensive experience.
Mind you, this advice is largely pertinent to those fifth wheel owners who have “electric over hydraulic” braking systems. When you hit the brakes in your truck – or hit the control lever on your brake control – electricity is run back to a motor in the trailer that, in turn, pumps hydraulic pressure to the trailer breaks. Conventional electric trailer brakes don’t react in this same way. If your trailer brakes are electric, the only completely assured safety when hitching up to keep it from rolling is to tightly chock the wheels – on both the front and rear of the tires.
An old-time truck driver told me that in years gone by when a semitrailer was parked, it often had no brakes until air was applied to the trailer. Today’s semitrailers have spring brakes that come on automatically if the trailer loses air, much like activating a breakaway switch on your towed RV trailer.
One last important step to remember on unhooking: Disconnect the umbilical cord once the king pin releases from the fifth wheel so you don’t drive away and pull the wiring apart.