Active route in compass mode

[oldjohn]

What happens if you switch between compass and gps mode without an active route?

Does activating the route in gps mode work ok?
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I have assumed that gps mode will not work without first activating a route as pypilot will not know which route to follow.  
My normal procedure is to use compass mode until the control is steady then activate a route and switch to gps mode. That is the procedure I have used with Raymarine and Simrad autopilots.