Heater blower inop.
Check fuses.
Then jumper the wires if necessary to run the blower with a 12V power
source you provide.
Then check power in vehicle harness is provided to the blower.
And ground is provided on the other wire.
Many vehicles also achieve blower speeds that are less than high or
max by using a resistor block that has preset resistors for each speed.
the resistors are mounted in the airstream of the heater case to let the
passing air inside the case keep them cool.
The resistor block may have a thermal limiter.
When it breaks from overheat, you must replace the blower and the
resistor block after testing and restoring connections and the problem
repeats after testing.
The switch connection may be checked if no problem found yet, and
the function control should also be inspected.
If access and testing must vary from this, the service manual must be
consulted because many systems are possible and in use.