diff --git a/homeassistant/components/device_tracker/tplink.py b/homeassistant/components/device_tracker/tplink.py
index 17beab02532..ad295099bf5 100755
--- a/homeassistant/components/device_tracker/tplink.py
+++ b/homeassistant/components/device_tracker/tplink.py
@@ -277,8 +277,10 @@ class Tplink4DeviceScanner(TplinkDeviceScanner):
         _LOGGER.info("Retrieving auth tokens...")
         url = 'http://{}/userRpm/LoginRpm.htm?Save=Save'.format(self.host)
 
-        # Generate md5 hash of password
-        password = hashlib.md5(self.password.encode('utf')).hexdigest()
+        # Generate md5 hash of password. The C7 appears to use the first 15
+        # characters of the password only, so we truncate to remove additional
+        # characters from being hashed.
+        password = hashlib.md5(self.password.encode('utf')[:15]).hexdigest()
         credentials = '{}:{}'.format(self.username, password).encode('utf')
 
         # Encode the credentials to be sent as a cookie.