Bad Safety Sensor Wiring Splice

Bad splices can be very sneaky.  The don’t always fail completely.  Instead, the wires end up essentially laying on top of each other, making contact until some slight vibration or movement (we are talking about microscopic changes here) causes them to come apart.  Even changes in temperature and humidity can be enough to break the connection.

The result is loss of power to the safety sensors, which leads to your garage door refusing to close.  It can be a constant problem, or may come and go at random.

It is easy to mistake a bad splice for an alignment problem (especially if you have a LiftMaster/Chamberlain/Craftsman opener), so be sure to do your troubleshooting in the right order.

Finding the Splice

Most homes built before 1993 were never pre-wired for safety sensors (since they were not required). So, the wire was added during the garage door opener installation, usually stapled to the wall or framing.  Trace the wires and you may find one or more splices that could be the source of your problem.

Most of the time the only splices you will find are near the safety sensors where they join the pre-wiring that runs through the wall.  They may be out in the open and easy to see.  But, its common for them to be hidden behind the drywall.  If the wiring that comes out of the ceiling over by the opener motor looks like a different type than the one that goes into the wall by the sensor, there is probably a splice that has been tucked behind the drywall not far from the safety sensor.  You can usually get it out by gently pulling on the wire.  But if the hole is small or has been sealed with caulk or spackle, you may have to enlarge the hole in the drywall to get the splice out.  If it doesn’t come out easily be very careful about tugging on the wire so you don’t pull the splice apart completely, leaving the end of the wire stuck inside the wall where you can’t work on it.

There may be another splice near the opener.  Sometimes the electrician doesn’t leave a long enough wire tail sticking out of the ceiling.  In this case you have to add to it in order to reach the wiring terminals on the side of the motor. Also, if the pre-wiring is extremely thick, a length of bell wire may be spliced to it in order to reduce the wire down to a size that will fit the terminal.  

Next:  Checking the Splice