diff --git a/mqttclient/fanATserial2mqtt.py b/mqttclient/fanATserial2mqtt.py
index 644ac69..62ae8ef 100644
--- a/mqttclient/fanATserial2mqtt.py
+++ b/mqttclient/fanATserial2mqtt.py
@@ -18,7 +18,15 @@ COMMAND_PREFIX = "ollpe"
 mqtt_server=os.environ['MQTT_SERVER']
 mqtt_topic=os.environ['MQTT_TOPIC']
 # SERIAL Port
-serial_device=os.environ['SERIAL_DEVICE']
+try:
+    serial_device=os.environ['SERIAL_DEVICE']
+except (KeyError):
+    # search serial device
+    for root, dirs, files in os.walk("/dev/serial/by-id/"):
+        for name in files:
+            abspath=os.path.join(root, name)
+            serial_device=abspath
+
 
 # Logging
 try: