The 1000-ohm, three-watt 4074FAB Resistor is used in certain applications to assure compatibility with power stealing thermostats.

Use this Resistor When Installing

  • Forced air systems using ST9120 or ST9141
    Electronic Fan Timer.
  • Taco zone valve applications.
  • Trane electric heat air handlers.
  • Oil systems using Honeywell R8184 Oil Primaries.
  • Cool only applications.


When Installing this Product

  1. Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.
  2. Check the ratings on the resistor to make sure the resistor is suitable for your application.
  3. Installer must be a trained, experienced service technician.
  4. After installation is complete, check out product operation as provided in these instructions.

Electrical Hazard.

Can Cause Electrical Shock or Equipment Damage.
Disconnect power supply before installing resistor.

To Install The Resistor

  1. Loosen terminal screws as shown in the application drawing.
  2. Slide the resistor leads under the terminal screws and tighten the screws.
  3. Turn on the system power.


  1. Set the thermostat heating setpoint to 10°F (6°C) above the room temperature.
  2. Watch the thermostat display for approximately five minutes to be sure the display does not go blank during the call for heat.
  3. Reset the thermostat to a comfortable setpoint.

Automation and Control Solutions
Honeywell International, Inc.
1985 Douglas Drive North
Golden Valley, MN 55422

Honeywell Limited
35 Dynamic Drive
Scarborough, Ontario
Scarborough, Ontario

Documents / Resources

Honeywell 4074FAB Resistor [pdf] Installation Guide
4074FAB, Resistor


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