Optical sensors probably causing garage door problem

Q: I have a problem with my garage door opener. When I push the button, it goes up with no problem. However, when I push the button for the door to go down, it comes down about a foot and then goes back up. If I hold the button down though, the door will close. I hope this won’t be an expensive repair.

A: Get out your checkbook. But instead of buying a new garage door opener, you can buy me dinner.

Actually, this is a cheap fix, and you probably won’t need to buy anything.

Your garage door opener is sensing there is an obstruction that will prevent the door from closing. This is usually due to a problem with the optical sensors. Usually, if the path between the sensors is unbroken, the door operates normally.

Let’s say a child is running under the door as it is closing. The child breaks the path between the sensors, and the sensors send a signal to the opener. When this happens, the automatic reversing mechanism activates and reverses the door. This is a safety feature designed to prevent injury.

The sensors are little black boxes about the size of a deck of cards that can be found on either side of the bottom of the garage door. There usually is a light on each sensor. One will have a green light that signifies power to the units, and the other will have a red light that signifies that the sensors are “seeing” each other (i.e., that there are no obstructions). Be aware that the lights may not be green or red but serve the same purpose.

If the red light is blinking, the sensors are not aligned. Realign them by moving one of them until the red light stays lit. The sensors are attached to the garage wall by metal supports, but they are easy to bend and reposition, if necessary.

Your problem also may be caused by the sun. If the sun shines on one of the sensors, it may hit it so that the sensor’s view is blinded. You can fix this by sticking a piece of cardboard in front of the sensor to block out the sun.

If the light still doesn’t stay lit, there may be a problem with the wires leading to the sensors. Check that the wires are securely attached to the sensors (there are two wires to each sensor). Also, check that one of the wires has not been cut; if so, strip off some of the insulation from the ends of the wires and reattach them.

Finally, get a ladder and check the back of the garage door opener unit to make sure that the wires are still attached to the terminals.

Mike Klimek is a licensed contractor and owner of Las Vegas Handyman. Questions may be sent by email to handymanoflasvegas@msn.com. Or, mail to 4710 W. Dewey Drive, No. 100, Las Vegas, NV 89118. His web address is www.handymanoflasvegas.com.