100A fuse - why?

[lwt]

This fuse often appears as a topic, usually when it has gone without warning and stranded some poor owner at night,in rain/snow/hail and on a roundabout/motorway/car park exit/ferry. When I looked at mine, the fuse was ok but the connections were loose so the plastic box was melting from the heat. So, what is it protecting and why is it 100A? Or to put it another way, why not uprate it to 150A or get rid of it altogether. Any views, or better still any facts?

Ian.

[leadfootlydon]

I'd like to know too, please.

[spend]

Early cars didnt have them, then Land Rover installed them.....

Move the fuse inside the cabin. Its arguably safer to run the wires (pre fused) over the head than have them (& the fuse / holder) anywhere near the heat of the manifolds....


Battery ======== Starter == Fuse ========== Alt
..........................||================================ Fuse box

becomes

Battery ======== Starter
||
Fuse box == Fuse ========== Alt

I saw this arrangement in a car and copied it, there are 4 x 9.5mm blade connectors in a 'bus' at the rear of the fuse box so it is an easy place to make the link between alternator & battery

I did::

Battery ======== Starter
||
Mega Fuse === 100 midi fuse ====== Fuse box
.........||
.........100 midi fuse ====== Alt

Just cos it was easier in my case (models differ a bit over the years) & only added because I uprated the Alt on an early car. There is plenty of room between battery and fusebox to 'stow' the big fuses at the opposite side to the ecu & its fuses.

The fuse box does have an integral fuse link which is normally covered in sealant, but this is impractical to use without a cover to the fusebox.

There are also better midi fuse holders than the ones used, I found some at my local auto electrician (they are the same make as the VWP Mega Fuses just the smaller size factor, but VWP didnt sell the midi/strip size?) However I dont believe any are produced to withstand the extremes of the position that TVR places them in.

Dave

[tesstickles]

One theory is that the fuse protects the car electical system if the alternator (which is a 100 amp thingy) should go pooof! There should be plenty of theads on the foum to search for.

[shpub]

If a short develops in the alternator, it stops the short from also short circuiting the battery which could result in a fire or even an explosion. The effect is like having an arc welder go mad. It was fitted for safety reasons.