Microchip PIC24 DAC output too low
Thanks for the effort. Here is the solution : 

DAC pin should be set to input :

TRISGbits.TRISG9 = 1;


(probably so as not conflict with DAC output)

Actual VREF+ can be alternated between A10 and B0 in configuration. Where leg 30 is probably AVDD and not VREF+ as in datasheet.

And it works correctly. With 2.4v reference it outputs 2.4v maximum. And with VDD=3.2v, and REF=AVDD or REF=VREF+  the maximum is 3.2v. As expected.