When the fan will only turn on at just one speed, it is due to a faulty blower motor resistor.
Many times when the resistor fails it will simply allow the full speed to work and not the other.
The blower motor resistor is mounted on the fan motor housing. It is located under the passenger side dash (see diagram).
First change out the resistor to see if fixes the issue with the light.
Please let me know of any questions.
Images (Click to enlarge)
Monday, September 20th, 2021 AT 12:36 PM