Blower resistor has failed. It is located behind the glove box.
blower motor relay
Usually the blower motor resister has gone bad.
On a 2007 Nissan Frontier, the blower motor resistor is typically located under the dashboard on the passenger side, near the blower motor itself. It is usually mounted to the HVAC housing. If the blower only works on high, the resistor may be faulty, as it controls the different blower speeds. To access it, you may need to remove a few panels or the glove compartment for better visibility.
Maybe a bad bearing in fan motor
replacing the blower motor resistor which cost about 20 bucks or so.....hope this helps
Blower motor resistor defective
When the fan is on high it does not run through the blower motor resistor. The low speeds don't work because the blower motor resistor is bad.
Check the blower motor resistor
The most likely problem is the blower resistor located behind the glove box door.
YOUR BLOWER RESISTER IS BAD
Blower motor resistor may need replacing
The blower control module has gone bad. Carquest has a new one for $20-$25 dollars.