Here are some actions that may help improve the connectivity of the wireless adapter:
1. Do a clean install of the most recent wireless driver. Make sure to uninstall and delete the previous driver before installing the new one.
2. Apply the configuration from the advisory: What are the Recommended Settings for 802.11n Connectivity?
* These settings also apply for Wireless AC.
3. Make sure your network is using a current Authentication Protocol, such as WPA2-AES. For testing purposes, you can try disabling authentication and test the connection again.
Let us know if this helps resolve the issue.