Fix timer switch in Sensibo (#96911)

homeassistant/components/sensibo/switch.py

@@ -151,9 +151,10 @@ class SensiboDeviceSwitch(SensiboDeviceBaseEntity, SwitchEntity):
     @async_handle_api_call
     async def async_turn_on_timer(self, key: str, value: bool) -> bool:
         """Make service call to api for setting timer."""
+        new_state = not self.device_data.device_on
         data = {
             "minutesFromNow": 60,
-            "acState": {**self.device_data.ac_states, "on": value},
+            "acState": {**self.device_data.ac_states, "on": new_state},
         }
         result = await self._client.async_set_timer(self._device_id, data)
         return bool(result.get("status") == "success")