Don't know all
changers but you would need a small single pole relay that has a operating voltage the same as your light. When the
changer powers the light it would also power the relay, which would close the contacts on the sensor and then the yolink
app would send you a push notification that your
changer is down. If your
changer is a
Hamilton I'd be tempted to buy the factory kit from Randy- that's a reasonable price and I assume it's plug and play.
You'll also need a hub at the car wash to connect to the sensor. You can install another Speaker hub at your home or office and it will speak to you and say "left carwash
changer is out of service" or similar if you like. All these devices that yolink sells range from 25-35 dollars and are pretty handy. You can also connect that relay above to pressure switches on your air and float switches on your tanks, etc.