Passenger side heater only works on high
blower motor resistor ?
My Corolla’s heater blower sports 3 speeds, works on the 2 highest speeds, but not the lowest. That speed failed after about 3 years. Pretty common problem on designs that use resistors to slow the fan speed. A 2017 Jeep may not use that technique though.
A somewhat related aside, I was recently doing some work under the my 50 year old Ford truck’s dashboard, and decided to see if I could find that resistor. I looked and looked, could never find it … lol … afterward I got to thinking it’s probably located inside the heater ductwork, that way the heat from the resistor helps heat the passenger compartment too. Plus it would tend to cool the resistor and make it last longer. It’s never failed on the truck.
When I encountered this problem in the past on my cars, replacing the resistor pack fixed it. I agree with @vipergg. Replace it and see if it returns variable fan speeds.