This listing is for a NEW a/c blower resistor (Replaces GM Part #3998401) for all 1970-1981 Firebird, Formula, Esprit & Trans-Am with factory air conditioning.
This is the part that mounts on the right-hand evaporator case half mounted on the passenger side of the firewall in the engine compartment. It helps regulate lower blower speeds.

TECH NOTE - The most common cause of failure of a blower resistor is a failed or failing blower motor.  Failure to correct this problem will burn out the coils and voide warranty of the switch.  This part does not control your high-fan speed.  If you do not have a high-fan speed, the high-fan relay and/or fan blower switch is the likely problem.