How to Wire a Hella 12V Relay

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Hella manufactures 12-volt relays designed for automotive applications. Relays use two voltage sources; a control voltage and load voltage. A user-operated switch turns the control voltage on and off. The control voltage then energizes the relays electromagnet. Once the electromagnet energizes, the load voltage enters the relays secondary circuit and continues on to the electrical device that the relay controls. When installed near the electrical device, the relay shortens the amount of load wire needed, which lessens the load wires voltage drop. Larger voltage drops affect the electrical devices performance and increase the chances of a switch overload.

Step 1

Strip one-half inch of insulation from each wire that will connect to the relay. Four-pin relays use four wires and five-pin relays usually use five wires. In some applications, five-pin relays omit the fifth wire.

Step 2

Slide the circular end of a wire terminal over the stripped end of a wire. Crimp the circular end of the wire terminal onto the wire with lineman pliers. Repeat this process for each wire.

Step 3

Determine which wire leads to the switch. Slide this wires wire terminal onto the Hella relays terminal marked "86" (see reference 2 under the common pin designations chart).

Step 4

Determine which wire leads to a ground source, usually the vehicles chassis. Slide this wires wire terminal onto the Hella relays terminal marked "85" (see reference 2 under the common pin designations chart).

Step 5

Determine which wire leads to the electrical devices power source. Often this wire leads directly to the batterys positive terminal. Slide this wires wire terminal onto the Hella relays terminal labeled "30" (see reference 2 under the common pin designations chart).

Step 6

Determine which wire leads to the electrical device. Slide this wires wire terminal onto the Hella relays terminal labeled "87." This terminal turns hot when the control circuit activates (see reference 2 under the common pin designations chart).

Determine which wire leads to the second electrical device, if equipped. Slide this wires wire terminal onto a Hella five-pin relays terminal labeled "87A." This terminal turns hot when the control circuit deactivates. Four-pin relays do not use this terminal (see reference 2 under the common pin designations chart).