No Heat

My car is a Grand Cherokee Limited 1996.
I don't what happen with my car. The AC unit working perfect but the heater not. i am open to any information o Tip(s). What i can do.
Thank you to all

does the blower run when in the HEATER position?

check the HVAC codes, I believe you push the recirc and AC button at the same time. and it should display the code(s).

may be low on coolant as well. a low coolant level will make you blow cool air because there is not enough warm coolant to properly circulate through the system. and yes, you can have a very low level and still not overheat the engine. especially in the winter.