A slack garage door chain can prevent your electric garage door opener from opening the door properly, if at all, and can damage the sprocket or internal gears of the unit. That's why you need to take a few minutes to adjust the chain to remove the slack; the job is simple, and anyone can perform it with a few basic tools. Below are the instructions, as well as a list of tools and materials you will need, for tightening the chain on your garage door opener.

Tools and materials needed

• One adjustable wrench

• Locking pliers

• Stepladder

Step-by-step procedure

1. Keep safety first - Working on garage doors is perfectly safe as long as you take a few important precautions. First, disconnect the power to the garage door opener by unplugging its electrical cord from the outlet; if it is an older opener without a plug, switch the relevant breaker off at the main panel. In addition, be sure to place your stepladder in a safe position when working on your opener, and never climb higher than the manufacturer's indicated limits on the steps. If you are using an aluminum ladder, be careful not to accidentally contact electrical wiring that might be in the vicinity. Finally, keep the door lowered while working on the opener and only open it when you are off the ladder away from the moving cables and parts.

2. Loosen the chain carrier bolt - Though your garage door chain may appear similar to a bicycle chain with its linked construction, it does not make a continuous loop. Instead, one end of the chain is attached to an adjustable bolt, which in turn is attached to the door trolley. The door trolley moves up and down the center rail, and it moves the door via its connection with the other end of the chain. If the chain links loosen over time due to usage and mechanical stresses, then you will need to draw up the slack by adjusting the bolt.

To loosen the bolt from the trolley, first remove the outer nut that fastens the bolt in place. Turn the nut counterclockwise to loosen it, but be careful not to remove the nut completely from the bolt; if you do, the bolt will slide out of the trolley and cause the chain to drop toward the ground, which could cause injury or damage.

3. Adjust the inner nut to tighten the chain - Next, you will need to tighten the inner nut to provide more room for the bolt to be pulled through the trolley mounting hole. Though that may seem counterintuitive, keep in mind that you are moving the nut back toward the opener, so you will have more available bolt length to pull toward the door. To move the inner nut backward, use your adjustable wrench to turn it clockwise.

Begin by moving the nut one-half inch backward from its original position. Then, grasp the shaft of the bolt with a pair of locking pliers and pull it and the chain toward the door until the inner nut is flush against the hole in the trolley. Observe the chain as it wraps around the sprocket on the opener, and verify that you have pulled enough slack so it fits snugly with just a slight amount of give when you push in the side of the chain. If you haven't removed sufficient slack, then move the inner nut another one-quarter to one-half inch toward the opener and check for a snug fit again.

4. Secure the outer nut - After you have adjusted the inner nut to a satisfactory position, you can tighten the outer nut so that it is flush against its lock washer and the trolley mounting hole. If there is no lock washer in place, be sure to obtain one that will just fit the shaft of the bolt; otherwise, the outer nut will slip over time and cause your chain to loosen again. To tighten the outer nut, use the adjustable wrench to turn it clockwise until it is securely in place and compresses the lock washer against the rim of the mounting hole.