Where does relay pin 86 connect?

Pin 86 connects to the black/blue wire in the kick panel, which goes to the dome light.

Which relay pins go to ground?

Both pin 85 and pin 30 connect to ground.

Is relay pin 87a used in this wiring setup?

No connection is labeled for pin 87a; it appears unused (shown grayed out).

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1990 Ford Bronco Alarm Relay Wiring Diagram - Dome Light Black/Blue Wire

Relay terminal wiring diagram with pins 30, 85, 86, 87, 87a labeled to alarm and ground

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Relay wiring diagram showing terminals 30, 85, 86, 87 and 87a with connections to the alarm wire, dome light wire, and ground.

AI caption July 2005 · Photo 87 of 97

This document is a simple hand-made wiring diagram showing how to connect a standard 5-pin automotive relay (pins 30, 85, 86, 87, and 87a) for an aftermarket alarm installation. The diagram shows the relay outline with its pin positions and the connection for each terminal: pin 87 connects to the negative alarm wire, pin 85 connects to ground, pin 30 connects to ground, and pin 86 connects to the black/blue wire found in the kick panel (the wire going to the dome light). Pin 87a is shown in the diagram (grayed out) but has no labeled connection, indicating it is unused. The diagram was uploaded to a 1990 Ford Bronco gallery, suggesting it documents how to trigger an alarm's door-input from the Bronco's dome light circuit using a relay. A reader can learn the exact relay pinout wiring needed to interface a negative-trigger alarm input with the black/blue dome light wire in the kick panel of the vehicle.

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Frequently asked questions

Which relay pin connects to the alarm's negative wire?: Pin 87 connects to the negative alarm wire.
Where does relay pin 86 connect?: Pin 86 connects to the black/blue wire in the kick panel, which goes to the dome light.
Which relay pins go to ground?: Both pin 85 and pin 30 connect to ground.
Is relay pin 87a used in this wiring setup?: No connection is labeled for pin 87a; it appears unused (shown grayed out).