from the basics you're giving, sounds like a bad switch. The cheapest and easiest fix is to go to the library, pick up a hanes manual, study how to remove the climate controls. Grab your tool box and go to a you-pull-it junk yard. Pull the part on a crashed car to give you practice with your own. Then do it in yours.
However, depending on the type of switch, you could just rebuild the switch by relubricating it and cleaning the contacts.
A bad control switch can cause your 2003 Nissan Sentra heater blower to stay on. The motor or a bad sensor can also cause the heather not to work properly.
you need a new blower motor resistor
The Nissan blower motor can be found in the engine compartment on the firewall. The blower motor will be on the passenger side of the firewall.
They are generally found close to the blower motor.
to the right of the gas peddal
Defective blower motor resistor pack.
More than likely the blower motor speed resistor burned out.
i am looking for the location of a heater blower resiter on a 1996 Nissan Serena
under passenger side
where is the blower motor on a nissan rogue
Locate the resistor under the dash attached on the blower motor housing. Disconnect the wire harness connector. Remove the resistor and install a new one.
By the clutch pedal two screws and a plug