Understanding the operation of LM219 Comparator
The LMx19 has an open-collector output.  If you look at Fig 6.1 - Functional Block Diagram in the TI datasheet, you will see that the output transistor can only pull the output towards Ground when Low, and lets the output float when not Low.  It cannot drive the output to either supply (well, if V- is tied to Ground it can drive the output to V-/Ground).