on my 2009 Acura RL, the air/heater blower will not blow air sometimes regardless of where I have the fan spead set. Sometimes I turn on the car and it works, but many times when I turn on the car it will not blow any air... What part would be causing this?

 

My blower was intermittent also. Turns out the wiring connection to the motor was loose. It ended up burning the wiring and connector at the motor. Mine was too late to save as I had to replace the motor and connector.
There is a Acura bulletin # 06-006 that addresses this problem. It may not be applicable to your year but it is worth checking. Apparently the wiring harness is too tight and causes this problem. A new sub harness is available P/N 04321-S0K-A00. I would check the connector at the blower motor.
I ended up replacing the harness, blower motor, resistor and relay,