apollo-636-250 Question: Jim in Texas would like to know: I have an Apollo opener with the 636 circuit board. The "free exit" sensor stopped working recently. How is the best way to test it to see what needs replacing? My thoughts are that the buried sensor is probably not the problem. I do not see any cut wires etc... so I think it must be something on the circuit board that is malfunctioning. I would appreciate any help you can offer me to troubleshoot the problem. Answer: Hi Jim, the easiest way to check would be to disconnect the free exit probe completely from the Apollo 636 control panel, then with a jumper short out the open command where the probe was connected, if the gates trigger and open then you have a bad probe if the gate does not trigger and open the check your power to make sure you have enough voltage stored in your batteries, if you do then the problem is on your board. Interested in purchasing the Apollo 636 circuit board? If you need more info, please feel free to give us a call at 1-800-803-8093.