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HR02 Heavy Duty 100-Watt Heater Blower Motor Reducer Installation Instructions

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This device is designed to reduce the voltage to power a 6 volt heater blower motor after conversion of the vehicle electrical system to 12 volts.

Step 1. Disconnect the battery from the vehicle. Always do this step as you don’t want to be working with your electrical system while the battery is connected. Never skip this step.

Step 2. Mount the resistor using the enclosed #4 x 3/8” sheet metal screws. For best and safest results, mount this resistor inside the heater metal air duct housing away from materials that may melt, such as plastics, and away from passengers. The resistor develops heat as a byproduct of reducing voltage.

Step 3. Using the enclosed blue terminals and wire, connect one end of the resistor to the blower motor.

Step 4. Connect the other end of the resistor to the heater blower motor switch output. This is a series or in-line connection. There is no polarity to this dropping resistor; you can connect either end to the heater blower motor, and it is not sensitive to positive or negative ground.

Step 5. Check your work to make sure that the resistor is not touching anything that could melt, and is mounted in a location away from passengers.

Step 6. Reconnect your battery.

Step 7. Turn on your heater blower motor and check the voltage between chassis and the heater blower motor while it is running. Voltage output from the resistor should be about 6 - 8 volts. A common question is, “Why am I getting 12 volts on both ends of the resistor when not connected to the blower motor, or when the blower motor is not turned on?” The answer is that this reducer requires a load to drop the voltage, so the measurement must be made when the blower motor is connected and on.

Step 8. The heater blower motor switch should operation with 12 volts without getting hot. If you have a switch that does get heat up after conversion, you have the exception. In this case you can mount the resistor before the switch by connecting one end of the resistor to a fused power source and the other to the switch.

  • The HR01 is only designed for use with a heater blower motor. For other applications, use these products:
  • Oil, Gas, or Temperature Gauges: SGR1 or MGR1
  • Windshield Wiper Motor or Horn: WHR1
  • Tube Radio: DR100W1R5
  • Power Windows, Seats, Convertible Top: VRWTS
  • Borg Warner Overdrive Solenoid: VRODS1

Vintage Auto Garage cannot be held responsible for blower motors damaged by using this device. Proper installation and voltage after installation is the responsibility of the end user. 90 day warranty is limited to the resistor itself. This is the only warranty express or implied. Not responsible for any consequential damage caused by this device.

Always be safe and disconnect your battery when working on your electrical system!!

Click here to download the full guide with images