Blower Motor Resistors - 2001 Chevy Venture

There have been MANY posts in the forums about the blower for the A/C or heater not working on one or more settings (only works on high, etc.) In most modern vehicles, the Blower Motor Resistors control the speed of the blower. 
Here is some information I gathered from a couple of repair manuals that might help in troubleshooting and repairing
any problems that you might have with your blower motor speed related problems.

Blower Motor System - Description & Operation

The blower system for the AC or heater includes the following major components:

  • The Blower Motor itself
  • The Switch
  • Three (3) fuses. Two are in the Fuse panel (inside passenger compartment): fuse #28 & fuse #46. The other fuse is in the under-hood fuse block, fuse # 29.
  • One (1) Circuit Breaker (#5 - inside passenger compartment), which is used in High Speed mode only.
  • The Blower Motor Resistor Assembly
  • All associated wiring & connectors (see schematic below).

Basic Operation: 

Power for the blower is supplied through the HVAC Blower Fuse (#28) and is sent to the blower speed switch. As the switch is moved from setting 1 through 5, more current is allowed to flow through the motor, for a higher speed.  This is because less resistors are in the path as the switch is moved to a higher number. 

When the switch is on setting 5 (High), all resistors are bypassed and a relay on the resistor pack is turned on. This provides power (12 volts) directly to the motor, through a circuit breaker. 

Other information:

  • The blower motor resistor assembly is mounted next to the blower motor, inside the HVAC module.  This is so that air will flow across the module to help keep it cool (it can get very hot).
  • If one of the resistors burns up (opens), only a few of the speed settings will work.

Here is the schematic for the Blower Motor Resistors and the blower system.  Click on it for a larger view.
Blower Motor Resistors Schematic

Van Home | Maintenance Index | Other Information | Forum| Donate