How to Test Breakaway Brakes on a Big Tex Custom Cargo Trailer
Picture two trailers leaving the same yard on a Saturday morning. On the first, the breakaway cable is clipped to a slot on the hitch head and the battery box has not been opened since spring; the driver kicks the tires and rolls. On the second, the driver runs three checks in order and does not pull out until the trailer brakes are felt through the truck. Only one of them knows whether the emergency brakes would work if the coupler let go at highway speed.
The second driver is working from Big Tex's single-tire trailer owner's manual, 2020 edition, plus the separate breakaway instructions that manual points to. What follows is a set of function checks, not a ceremonial yank on a cable, and every condition here is tied to that manual: a trailer equipped with brakes, and electric brakes where the controller pull applies. Another make or model needs its own paperwork; this article does not speak for it.
What the Breakaway System Must Do
A breakaway system exists for exactly one scenario. If the trailer is equipped with brakes, the manual states that it carries a breakaway brake system that can apply the trailer brakes if the trailer comes loose from the hitch ball for any reason. That is the entire job: apply the trailer's own brakes after the connection to the tow vehicle is gone.
A battery and a cable together: the reason the system carries both is the same. A separation takes away the electrical path from the truck, so whatever applies the brakes has to be stored on the trailer and released by a mechanical pull. Which means readiness is a property of the trailer alone — charge in the battery, integrity of the rigging, a cable that can carry the pull through to the actuator. None of it can be borrowed from the tow vehicle at the moment it is needed, because the tow vehicle is the part that just left.
Every check that follows traces back to that fact. You are testing the only brake function the trailer has left once it separates.
Connect the Cable to the Tow Vehicle
Attachment comes first, and the manual is blunt about it: the breakaway cable must be connected to the tow vehicle, and not to any part of the hitch. Clipping it to the coupler or to a bracket on the trailer side is the shortcut that quietly defeats the system, because the cable then rides entirely on the side that is supposed to break away.
Work through the geometry. The cable has to pull a pin or a switch on the trailer when the trailer and the truck move apart. If both ends of the cable ride on the trailer side of the coupler, a separation moves them together, the cable goes slack, and nothing actuates. Which means the attachment location is part of the test, not a cosmetic detail you handle while hitching up.
Where exactly on the tow vehicle the cable anchors is a question the separate breakaway instructions and the tow vehicle's own documents settle. What the trailer manual settles for you is the negative: the hitch itself is off limits, however convenient it looks.
Check Battery and Rigging Before Towing
Condition is the second gate, and the manual sets it plainly: the breakaway brake system, including battery, must be in good condition and properly rigged to be effective. Two clauses carry the weight. A charged battery with a disconnected or misrouted cable is not properly rigged. A perfect cable on a battery that will not hold charge is not in good condition. The system needs both at once, and either one alone proves nothing.
Follow the energy. The breakaway battery is the only thing that can move the actuator once the trailer is loose, so a dead battery makes every downstream part irrelevant — the mechanism can be flawless and still do nothing. Which means the pre-tow check has to confirm the power source and the rigging, rather than the presence of a battery box under the tongue.
Suppose that battery last saw a charger in April and the trailer sat outside through a wet summer. Nothing about a tidy-looking box tells you what it will deliver in an emergency. The manual does not hand out a voltage number or a replacement interval, and this article will not invent one; the conditions it does give are good condition and proper rigging, and the actuator document behind them is where the hardware-specific detail lives.
Run the Low-Speed Controller Pull Test
Third gate: prove the brakes actually apply. With electric brakes, the tow vehicle carries a brake controller that sends power to the trailer brakes. The manual's instruction is to operate that controller while the truck tries to pull the trailer, before any road towing, at less than 5 mph, working the controller manually from the cab. What you are after is the operation of the trailer brakes making itself felt.
Here is where people fudge it. They glance at a display, click through a menu, or lean on the fact that the brakes worked last season. At a walking pace, with your hand on the manual control, what you want is the trailer tugging back against the truck. Feel it, or the check did not happen.
The physics explain why the speed matters. At a crawl, the truck can pull against applied trailer brakes and produce a clean, felt signal instead of a skid, and the driver can tell the difference between drag and nothing. Because that signal is a felt one, a static inspection cannot substitute: a trailer parked on level ground tells you nothing about whether current is reaching the brakes. The controller pull is the only step in the sequence where the driver applies the brakes from the cab and judges the result by feel.
Know When to Stop and Repair
A test with no consequence is theatre, so the manual pairs it with a hard stop: before towing the trailer, test the function of the breakaway brake system; if it is not working, do not tow — have it serviced or repaired.
That is a binary gate, and it should be. A trailer that fails the check carries no backup brake function for every mile that follows, and the gap shows up at the worst possible moment, after a coupler problem nobody planned for. Because this is an emergency circuit, probably fine is not a state it can be in. Which means the call gets made in the yard, not on the shoulder.
A partial pass counts as a fail. Cable attached correctly but battery flat, or battery healthy but the controller pull produces nothing the driver can feel — the system has not passed. Have that one item serviced, then run the whole sequence again before towing, not just the gate you touched.
Find the Separate Breakaway Instructions
What the owner's manual gives you is a gate and a pointer, not the complete procedure. It tells owners they will have a separate set of instructions for the breakaway brake, and it directs them to the axle and brake and brake-controller manufacturers' instructions to insure safe brake performance and synchronization. If those documents are missing, the manual gives Big Tex's number for a free copy: (903)575-0300.
Splitting it up has a reason: the trailer manual cannot see your hardware. Actuators differ, controllers differ, and one sequence written to cover every combination would be wrong for most of them. Which means the actuator-specific step — the release, the reset, the items the maker wants verified — belongs in that separate breakaway document, while controller setup and gain belong in the controller's own instructions.
For a buyer adding a trailer to a fleet, or a tech taking one over, the practical consequence is this: those two documents should travel with the trailer, not sit in a folder at the office. A pre-tow routine that depends on paperwork nobody can locate degrades into a guess within a month.
Build a Repeatable Pre-Tow Check
Turn the manual's three gates into one short routine. The cable goes to the tow vehicle, never to any part of the hitch; the breakaway battery and rigging get confirmed rather than assumed; the controller gets worked manually from the cab at less than 5 mph, and the trailer brakes are felt through the truck. Those are the manual's conditions in the manual's order, and each one ends in a pass or a stop.
Suppose you run four trailers out of one yard and rotate drivers weekly. The routine is worth writing on a card and taping inside the tongue box, because the middle gate is the one that decays quietly — a battery that sat, a cable that got rerouted during a repair. Assigning a named person per trailer per week is a management decision, not a manual requirement; what the manual requires is that the check happens before towing and that a failure ends the trip.
The question readers usually arrive with deserves a straight answer: these checks do not transfer to a trailer of another make, or to one whose brake setup is not electric. The Big Tex single-tire gates are written for trailers equipped with brakes and, for the controller pull, electric brakes; a different system needs that trailer's separate breakaway instructions plus its own axle and controller documents. What carries over is the habit of asking those questions in that order, and the refusal to talk yourself past a failed one.