I already had a few of these on doors and just got some more as part of a lot I bought, so I thought I'd add some to windows now. I have several windows that open as two separate panes, so I thought it would be convenient to use the external sensor option on the modules to monitor both panes with one 2843-222. I want to get an "open" condition if either pane is open. These modules have two screw terminals to add an external set of contacts but upon reading the documentation, the screw terminals are in parallel with the internal normally open magnetic reed switch. This means that both window panes would need to be open to have an "open" condition. Hardly useful, especially with most magnetic reed switches being open when no magnet is present. 

So I looked around on the web for a modification to have the switches in series (surely, I can't be the only one wanting this!). I didn't find anything, and the Insteon support forum has been down for a while. So here is my own little mod to get this functionality. It involves cutting a trace, cutting one lead of the reed switch, and soldering in a wire.

Dismantle the circuit board from the case (remove two screws) and turn it over to see the underside. Position it vertically, with the negative battery terminal at the bottom. Be careful not to break anything when sliding the negative battery terminal off the plastic mount.

Step 1: Cutting a trace. Ignore the yellow wire for now. On the underside you will see one trace going from JP1 to the screw terminal on your right. Cut it near the screw terminal using an xacto knife or something similar. It's a good idea to verify that continuity from JP1 to the screw terminal is indeed cut, using a multimeter.

 

Step 2: Cutting reed switch lead. Flip the board over to see the component side (with the screw terminals still at the bottom). Cut the top lead near where it enters the hole in circuit board, then bend it a bit, towards the center of the board. Because the reed switch is now held to the board by just one lead at the bottom, I put a small dab of hot glue to help in keeping it in place.

 

 

Step 3: Adding a wire. Add a small wire (I use wire wrap wire) from the screw terminal that was isolated in step 1 (that's the yellow wire), through a hole, and solder it to the free end of the reed switch that you bent towards the middle in step 2. Don't go through the screw hole! There is a convenient smaller hole near JP1.

 

 

 

That's it! Now, both the internal reed switch and an external switch (or several, in series) are in series and have to be closed to get a "closed" condition.

If you ever need to use this modified module without an external sensor, now you'll need to put a small jumper wire between the screw terminals to bypass the missing external reed switch.

Put it back together and enjoy.

 

I might add that an alternative to making this mod would be to use only external magnetic contacts (wired on series) connected to the screw terminals, and mount the open close sensor module itself nearby, but with no magnet near it. This would leave the internal reed switch open, allowing just the external wired ones to work.