How to Wire a Lucas Alternator

by Stephen Benham
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Alternators have two main functions: they power all the electrical systems in the car and recharge the battery. Lucas alternators are practically maintenance-free and can be expected to operate for between 120,000 and 150,000 miles before they need attention or replacement. Unlike generators, the brass rings that the brushes make contact with are completely smooth, and the brushes are made out of graphite. Wiring a Lucas alternator is a fairly straightforward process, but some car manufacturers do position alternators in hard to access places.

Step 1

Open your car's hood and prop it up. Disconnect both battery cables from the battery with a wrench and tuck them away from the battery terminals before proceeding.

Step 2

Locate your Lucas alternator, which is made of aluminum and has vented sides through which you can view coils of brass wire. It is attached to the engine with two static bolts and an adjustable bracket. The fan belt will go around the pulley wheel that drives the alternator.

Step 3

Find the alternator's terminals. There are many types of Lucas alternators: some have two terminals while others have up to four. If you have two terminals, one is positive, the other negative, and they are labeled or colored. If you have three terminals, one is negative, and two are positive. If there’s a fourth terminal, it will be smaller than the others and connects a wire that goes to your dashboard to indicate the alternator is operating correctly.

Step 4

Check the type of terminals. Many Lucas alternators have spade-type connectors, making it easy to attach the cables. Others have screw bolts, and the cables attach under them. If your alternator has screw bolts, use a small wrench to loosen them then carefully remove them as they can easily fall into the engine compartment.

Step 5

Connect the negative cable to the negative terminal of the alternator. The cable will be black, and the opposite end will attach to your car’s body as it also acts as the ground. Either push the connector onto the terminal or place the eyelet onto the terminal and screw the bolt in with your fingers. Tighten the bolt with the small wrench.

Step 6

Attach the positive cable to the positive terminal of the alternator. If your alternator has two positive terminals, one connects a cable to the starter motor, and the other connects the cable that goes to your battery. Locate the two positive cables nearby: they will be red. If your car only has one cable, then the wiring for the starter motor is elsewhere, and you do not need to use both terminals. Push the connectors onto the terminals or position the eyelets over the terminals, then screw the bolts on with your fingers. Tighten the bolts with the small wrench.

Step 7

Locate a yellow wire if your alternator has a fourth terminal. If you do not have another wire, then ignore the terminal as your dashboard warning light is wired elsewhere. The fourth terminal is smaller than the others and so is the wire. Push the yellow wire onto the connector or place the eyelet over the terminal and screw in the small bolt. Tighten the bolt with the small wrench.

Step 8

Reconnect the battery cables to the battery. Ensure the positive cable is attached to the positive terminal and the negative to the negative terminal. The cables are colored red and black, and the terminals are also clearly labeled. Close your car’s hood.

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