[Lee]

Originally Posted by JRTJH

If you think about how the emergency braking system actually functions, there's a "perfect storm of events" that must occur BEFORE the brakes will activate. First, when the trailer separates from the ball, IF the safety chains hold, a SECOND event must occur. The plunger on the break-away switch must be pulled. Far too many people don't cut/shorten the plunger cable, so effectively, if the "OEM cable is used as supplied at delivery" chances are very good that it will not function as expected.

In theory (yeah I know) the way it's supposed to work is this:

The trailer separates from the ball.
As the trailer moves back, the break-away cable tightens BEFORE the chains reach full extension and the plunger is pulled.
The break-away switch closes, applying braking action using onboard battery power. The reason for this is that there is no assurance that the 7 pin umbilical will remain connected to the tow vehicle AND, if the safety chains do not hold, that connection will definitely be severed.
The brakes slow the trailer and prevent it from "overrunning the tow vehicle" preventing increased damage and helping to maintain control by not "banging into the back of the tow vehicle" as you attempt to slow/stop the rig.

If the safety chains are shorter than the plunger cable, the trailer brakes won't function. If the 7 pin umbilical cable is shorter than the safety chains, it will sever BEFORE the chains reach full extension and remove any power from the tow vehicle that might reach the trailer brakes. If the plunger cable is too long, you have an increased risk of the trailer slamming into the back of the tow vehicle, causing loss of control and increasing the chances for injury.

In the event of a separation, you want the trailer brakes to hold the trailer back from the tow vehicle as you slow to a stop. If it "works as planned" the safety chains will keep the trailer in line with the tow vehicle, but don't count on the 7 pin umbilical to remain connected.

In the event the safety chains fail, then you definitely want the onboard battery to power the trailer brakes to slow the "runaway trailer" before it slams into an oncoming vehicle or sideswipes a vehicle going in the same direction.

So, it may be a good idea to think through the actual sequence of events that occur, inspect your plunger/cable assembly to be sure it is shorter than the safety chains and that the system actually works as expected.

ADDED: While I'm sure there are "some" I've not yet, in 50 years of towing and being around RV's, seen a dealership that cuts/shortens the break-away plunger cable so it "fits" the tow vehicle/safety chain/hitch for that application.... My guess is that probably 50% of the break-away cables in use by members on this forum are 'too long to pull the plunger' if the trailer separates from the ball or from the fifth wheel hitch.

Excellent and VERY important post!!!!!!

In all my years of towing TT's I never realized the importance concerning the length of the break-away cable's length..... I know for a fact the cable on my TT is way to long...... And it will be shortened to correct length before it's ever moved again!!!!!!!

Lee