What should the voltage be at my garage door opener sensors?
The voltage to the sensors is usually transformed at the main opener to “low voltage”, probably DC but maybe AC. Usually 12 volts DC, so your 13 volt reading is likely correct. Once inside the sensor, hard to say what the electronic board is doing with the voltage once it is fed in. The rating plate or sticker on the opener should have some reference to the “low voltage” to the sensors. Regardless, if you’ve got the proper voltage at the opener and down the circuit to the sensors, it would be a safe guess to assume either the sensor(s) are bad or the negative side isn’t connected properly.
