Queries aren't routed, the entire connection is. The connection does not change based on the type of query executing on that connection. You will connect to the Listener in either read-write (default) or read-only mode (called the "Application Intent"), and the Listener will route that connection to the proper instance.

Have you set up Read-Only Routing to specifically send read-only connections to the AG's secondary instance? The default is to send all connections only to the primary.

Are you setting the optional Application Intent property of the connection string to ReadOnly before you connect? All connections by default are read-write, and will go to the primary.

To connect SSMS2014 to an AG Listener in read-only mode (and be routed to a read-only secondary if that has been configured):

1. In the "Connect to Database Engine" box, click the 'Options >>' button, then click the 'Additional Connection Parameters' tab.

2. In the large text box provided for additional connection parameters, type ApplicationIntent=ReadOnly;

Note that all applications you wish to use the read-only secondary must also explicitly set the ApplicationIntent connection property to read-only at time of connection, or they will always go to the primary.

This MSDN guide on troubleshooting AG configuration may help: https://msdn.microsoft.com/en-us/library/ff878308%28v=sql.120%29.aspx#ROR

-Eddie