Lock your (not so new) car with Smartthings/Homeseer/HA etc

Lock your (not so new) car with your smart home

A simple way to lock your car using your smart home. Involves a very small amount of soldering or a strategic tape/glue job. No high voltage

Note: I am not liable if you break your stuff or hurt yourself. But this is a beginner to medium level easy setup though. This could technically be used for unlocking, starting, open trunk, and alarm but since there is no status reporting of whether or not you started the car, if the car was in the garage and you started it accidentally you wouldn’t know. So I would suggest NOT doing that


  1. A Key fob that is already connected to your car.
    Model used: NAH2503
  2. A dry contact relay. There are many companies that makes these.
    Model used: Zooz Z-Wave Plus S2 MultiRelay ZEN16

Simply connect the key fob like the attached diagram shows. (you don’t need Switch 3)


  1. Open the key fob casing. NAH2503 has one screw and then use a flat pry to pop it open
  2. take out the internal chip and look at the buttons.
  3. If your buttons looks similar to the NAH2503 and if it is just a simple metal contact this should work for you (NAH2503 requires removing the top plastic layer and the metal button actuator. Shown in picture)
    (you can test by making a quick metal connection between the outer ring and inner dot)
  4. connect the outer ring of the button to wire #1 (solder/tape/glue)
  5. connect the inner dot of the button to wire #2 (solder/tape/glue)
  6. connect wire #1 and wire #2 to the relay (R1 or R2 or R3. I used R3)
  7. connect the relay to your smart home. I am using homeseer now, but thought I would post here too. Just download the DTH for Smartthings.
  8. You now want to ensure the relay is set to a do a single short connection and turn off after a second. This can be done by enabling Garage door mode on the relay.
    for Zooz Zen16 the parameters to change are:
    R1/Sw1 = Parameter 2 , Value = 3 = Garage door mode for switch one
    R2/Sw2 = Parameter 3 , Value = 3 = Garage door mode for switch two
    R3/Sw3 = Parameter 4 , Value = 3 = Garage door mode for switch three (only need to set this one in example)

Since the ZEN16 relay module has 3 relays. I am using 2 for my garage doors, and the third to lock one car door

Zooz Z-Wave Plus S2 MultiRelay ZEN16


Very nice. I thought about doing something similar to this using an Arduino device connected to a dry contact relay soldered to the key fob contacts and then figuring out how to integrate that with SmartThings but this is a much simpler approach, I’m definitely going to look into doing it this way now.

Thought it was worth sharing being so simple. With these dry contact relay devices you can do a ton of stuff…

Side topic but you can do things like make your non-smart smoke/co2 detectors smart by adding something like this and 2 relays (smoke/co2) (different kind of “relay”) from the brand that makes your smoke detectors (kidde, brk/firstalert)

Cost about $100 instead of replacing all the detectors. And when you do need to replace the detectors, the relay(s) will still work if you stick with the same brand. And they will follow electrical code, which is why I can’t use NEST smoke alarms technically