Defender Fusebox Upgrade

Replace the awful glass fuses with proper ATO blade ones.

The Defender (and the Series before it) suffer from awful glass cartridge fuses which seem to be quite unreliable, with the added bonus that they can't really handle much more than ~15 amps continuously without getting hot and either melting the fuse-holder or blowing. Land Rover get round this by simply not fusing some circuits. Yes, that's right, some circuits on Series & Defender are not protected by fuses. That could really ruin your day.

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Thankfully it's not very hard to upgrade to something better.

You will need:

Step 1

Disconnect the battery! It just makes life so much easier when you can swing tools & wires around with gay abandon without starting an electrical fire.

Step 2

Remove the fusebox cover, then unclip the old fuse holders from the metal panel.

Step 3

Unbolt the panel, carefully remove it - you'll likely need to unclip the flasher unit and possibly the intermittent wipe unit from the back of it so don't just yank it off.

Step 4

With the panel on the bench you can hopefully see fairly obviously what needs to be done to make the FBB8U's fit:

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I found that the bottom end of the FBB could just sit in the folded lip along the bottom of the panel if you pop the brass insert out of the plastic holder:

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Step 5

Fettle the hole with your angle grinder / hacksaw / file until the FBB drops in nicely.

Step 6

Mark & drill the two holes to hold the FBB in place.

Do not bolt the FBB to the panel yet - the next steps are easier if you leave the FBB's loose and attach the panel when done

Step 7

This is where things get serious - you now need to swap wires from the old to the new. Do this CAREFULLY, avoid pulling the wires, always pull the connector body itself. Some may find it helpful to use needle-nose pliers, gentle wiggling, muttered oaths, and overt threats.

It is a really REALLY good idea to move ONE CONNECTION AT A TIME from the old to the new so you don't lose track of what goes where.

You'll find it most convenient and comfortable to assume a position something like this:
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Step 8

When everything's moved across, THEN you can re-attach the metal panel, replace the flasher unit etc. on the back and carefully bolt the whole thing back in place, taking care not to trap any wires behind it or between it and the bulkhead.

Step 9 - You're not done yet

Think you've finished eh? Think again! Remember what I said at the top about Land Rover not fusing some circuits? Well, although you now have better fuses on all the circuits, you haven't added any new ones, which must mean there' still some un-fused circuits out there waiting to burn your car to the ground.

I haven't done exhaustive research on this but the main point lacking a fuse is the main battery feed from the engine bay into the vehicle - this comes in on the small multi-plug from the engine loom (picked up from the starter motor B+ post if memory serves) through the bulkhead and feeds everything “inside” the vehicle including the fuse box (via the ignition switch).

Now, as it happens, the connector on ours was corroded and I needed a feed for the electric fans, so I picked up a 4-way fusebox and bolted it to the bulkhead with a shiny new feed, taking two 20A fused feeds from it as the feed to the “inside”. Hopefully that means everything inside the vehicle can draw at most 40A before something goes pop.

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End Result

The untidy blue wire is the remnant of the previous owner's electric window install, now removed.

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alfie/fusebox_upgrade.txt · Last modified: 2016/04/22 13:42 by jin
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