Using Blue Sea Systems' Battery Switch AFD Terminals to Indicate Switch Position

June, 23 2006

Alternator Field Disconnect (AFD) is a feature of some battery switches—for example, Blue Sea Systems’ e-Series ON/OFF (PN 9004), HD-Series ON/OFF (PN 3001), e-Series Selector (PN 9002), and HD-Series Selector (PN 3003). AFD protects the diodes in the alternator if the battery switch is switched to the OFF position while the engine is running.

When not used to protect the diodes in the alternator, the AFD connections can be used to indicate when the battery switch is in any position but OFF—ON for the ON / OFF; 1, 2, BOTH for the Selector. The AFD switch is closed whenever the main contacts of the battery switch are in any ON position. Various indicators can be connected to the AFD terminals, such as lights, bells, or sound systems which will be activated only when the cross-connect switch is ON. This can be crucial if the battery switch is located in a remote location or otherwise not visible.

The AFD switch circuit should be limited to a load of 5A or less.Directions:

  1. Connect the anode side (+) of the LED to the AFD terminal (F1).
  2. Connect the cathode side (-) of the LED to the system negative.
  3. Connect the battery positive to the AFD terminal (F2).

  4. ON/OFF


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