If you have a box truck you use for deliveries, then the overhead door may be opened and closed many times each day. This constant use can lead to many maintenance and repair needs, One of the common repairs required is, cable replacement, due to a broken or frayed cable.
The cables work in conjunction with the drums and counterbalance springs to allow you to easily open and close the overhead door.
If you have a broken cable, then the counterbalance springs are not properly assisting in the opening and closing of the overhead door.
If only one of the cables is broken then the door will be heavy and difficult to lift, and you must be careful to keep the door level while opening and closing the door. If both cables are broken, then you have likely lost all the tension on the counterbalance spring and you will be lifting the entire weight of the door.
Replacing the cables is probably not a project for you to complete yourself, if you do not have experience and training for repairing box truck overhead doors.
The process for replacing the cable, depending on the type of system you have, will require unwinding the springs before replacing the cables, and rewinding the springs after cable replacement. The two primary spring systems you will see are Whiting or TODCO, and each one has its own unique process for winding and unwinding the springs. It is important to know which spring system you have and the proper procedure for completing any repairs safely.
When completing repairs on a box truck overhead door it is important to have a helper, so in the case of an emergency you do not get trapped inside the closed box and to be sure no one attempts to drive or move the truck while repairs are being completed.
It is important to know that even though the spring systems on box trucks are very similar to regular residential and and commercial overhead door spring systems, the process for installing them and doing repairs to the system is not exactly the same. An example of the difference is that Whiting two spring systems have the drums attached to the springs, and when the springs are rewound, they are wound down instead of up. The Whiting system uses a different procedure for setting the cables and the drums and then winding the springs. Whiting procedures also call for the springs to be wound with the door in the open position, and the door must be clamped in place to prevent the door from falling while repairs are being made.
Using the proper tools, parts, and procedures for box truck overhead doors, just like any other overhead door is critical. If proper techniques, tools and parts are not used, serious injury and even death can occur. Contact a trained and qualified repair technician to maintain and repair your box truck overhead door.