S30 Fuses and Fusible Links

What a Fusible Link Is

A fusible link is a short piece of wire that is a few sizes smaller than the wire it protects, with special insulation that won't catch fire. If something shorts to ground, the link melts before the big wire behind it can overheat. It does the same job as a fuse, but it can carry a large current for a short time (like the starting surge) without blowing.

On the 280Z the fusible link holder sits on the relay bracket on the right inner fender of the engine compartment, next to the voltage regulator and the ammeter shunt. The battery cable at the starter feeds it with a white (W) wire, and the main feed into the car leaves it as a white wire with a red stripe (WR). The 280Z also has a separate fusible link for the fuel injection, connected between the battery positive cable and the EFI harness.

From the 1975 280Z factory service manual, section BE, page BE-6. The 1975 headlamp and meter circuit diagrams show their power coming through the black link. The AWG column is our closest conversion.

Checking a Fusible Link

• Symptoms: several unrelated things stop working at once, for example the headlamps and the gauges, or the whole car is dead even though the battery is good. The factory headlamp troubleshooting chart lists a burnt fusible link as the first cause when neither beam works.
• Look and feel: a melted link often looks swollen or discolored. Squeeze it gently along its length. The factory manual says a melted link can be found by finger-tip inspection: if it feels soft or stretchy in one spot, the wire inside has melted.
• Test it: if you're not sure, check it for continuity with a meter or test light, the same as a fuse. With the battery connected, you should have battery voltage on both sides of the link.
• Find the cause first. A link only melts when a main power or high-current circuit has shorted. Find and fix the short before installing a new link, or the new one will melt too.

The Fuse Block

The fuse block is under the dash on the passenger side, on the relay bracket with the horn, defogger and wiper relays. Each pair of fuses shares a power source, printed on the fuse block cover. Here is the layout for the 1975 280Z:

From the 1975 280Z FSM, section BE, page BE-5. The "amp meter" feeds come from the main power wire through the ammeter circuit, not through the ignition switch. Fuse layouts changed between the 240Z, 260Z and 280Z years, so always go by the cover on your car or the FSM for your year.

Checking Fuses

1. Look first. A blown fuse usually shows a broken element. If you can't tell, test it for continuity with a meter or test light.
2. Check the holder too. On a 40-year-old fuse block the clips corrode, and a good fuse in a dirty clip acts like a bad one: the circuit gets low voltage, and the clip gets hot. The factory manual says to clean rusty or dirty fuse holders with fine sandpaper until you have clean metal-to-metal contact.
3. Feel for heat. After running a circuit for a while (headlamps are the usual one), a fuse or clip that is warm to the touch has a bad connection. Melted or brown plastic around a fuse is the same problem, gone further. See Fuse Block Problems.
4. Find the cause of a blown fuse before you replace it.
5. Use the right rating. Never install a fuse larger than the factory rating. A bigger fuse just moves the failure to the wiring.

Tips

• Headlamps load the fuse block. On the S30 all the headlamp current goes through the light switch, the combination switch and the fuse block. A headlight relay kit takes that load off and is one of the best things you can do for an old fuse block.
• Adding accessories: don't tap into an existing fuse for something new. Run a new fused wire from the battery or a relay instead.
• Keep spares. Keep a few 10A and 20A fuses in the glove box.