First, unplug and remove the battery, open the casing of the garage
door opener remote control. Some units use screws and some are held together with
Once you get the circuit board out, locate the pressure switch that
activates the circuit. With an ohmmeter, test the metal terminals on the circuit
board where the switch is located (most have more than two pins). You have to find
two solder joints that get "connected" when the switch is pushed. If you
are 100% sure you got the right tabs, hook up the battery to the remote and short briefly
the two tabs with a wire. If the garage door opens and closes, you have found the
Solder a wire to each of the two terminals at the switch in the
circuit board. Be careful not to damage any components or short out any traces on
the circuit board.
Mount a switch somewhere on the dash or console to operate the
remote. Solder the two wires that bypass the remote control's switch to the external
Build the circuit on the diagram (left) to step down the voltage from the
vehicle's 12 volts (the circuit works for up to 35 volts) to 9 volts. Make sure that
the battery plug is soldered BACKWARDS to the circuit (black to +12v ignition and red to
ground). Once the circuit is built, hook it up to the car's ignition (key on) output
and test output voltage and polarity with a voltmeter.
If the voltage is 9 volts and polarity is correct, plug up the
voltage regulation circuit to the remote's battery terminal. Test to make sure
everything works. Wrap up the circuit in electrical tape or heat shrink to avoid
shorts. Finally, hide the remote under the dash or somewhere else.