installing a main fuse

tim wood · Post by **tim wood** » Sat Dec 29, 2012 12:43 pm

Hi all,
as my car moves further from standard i'm thinking of installing one of those high rated fuses (around 60amps) into the main feed leading from the battery. Not the supply to starter of course but in the other lead. I no longer have the 4TR so this would seem to be the ideal place to locate the fuse block. Although I think any new circuits fan etc are suitably protected I do worry about high currents.

Has anyone done this mod or have any thoughts ?

Am I mad.....

thanks
Tim

MarekH · Post by **MarekH** » Sat Dec 29, 2012 4:24 pm

Dear Tim,

What exactly is a 60 amp fuse protecting?

The 60 amp fuse isn't a "fuse" - it'll just be a piece of hardware which will one day be next to a melted wiring harness. A more sensible task would be to unplug all of the wires one by one and measure how much current they use in steady state conditions, plus a list of which ones are inductive (i.e. have a large switch on/switch off current spike). Armed with such a list you can then REDUCE the fuse ratings on the whole car and thus have a much earlier warning of which components are failing.

Smaller, per item, fuses will not only limit the current better in an unanticipated overload situation, but will tell you where the problem is.

kind regards
Marek

Post by **1954Etype** » Sat Dec 29, 2012 4:29 pm

Bearing in mind that the largest fuse is 50a (horns) not sure what a 60a fuse will protect. Would a better idea be to fit relays and LEDs to reduce loads?

paulj · Post by **paulj** » Sat Dec 29, 2012 5:30 pm

Hi
I presume you have some concerns with the original fuse arrangement
so was i, the best protection would be to measure the consumption of each circuit and fuse accordingly.
a lot of circuits use the same fuse ideally each should have its own fuse
I just ended up using an isolator on the battery the type with a fuse,rated to run alarm and radio memory.
also if you try and start the car Isolator unscrewed. the starter just blows the fuse,
at least it gives good protection when the cars not used.
Regards Paul

mystery type · Post by **mystery type** » Sat Dec 29, 2012 5:33 pm

or have any thoughts ?

one of the first jobs i do on any old car is to install an isolator switch.
you can never be sure of these old wiring harness`s until its to late.

Its nice to know should i need to disconnect the power in a hurry, a quick twist is all that's required, plus this gives me piece of mind every time i leave the car unattended.

tim wood · Post by **tim wood** » Mon Dec 31, 2012 12:15 pm

thanks for all your replies guys. i've been thinking on this and looking at the wiring diagrams so usefully segmented by Coventry Auto Components.
The system uses some feeds which appear not to be fused at all.
Would this still be safe practice in the modern world?

Tim

Post by **Heuer** » Mon Dec 31, 2012 12:49 pm

tim wood wrote:
Would this still be safe practice in the modern world?
Tim

No, but then the E-Type would not be deemed safe in its entirety - no ABS, no airbags, no collapsible steering wheel, no traction control, no interior padding, no side impact protection, no headrests, no engine intrusion protection, no structurally rigid seats. Fuses are the least of your worries!

christopher storey · Post by **christopher storey** » Mon Dec 31, 2012 2:42 pm

When I was rewiring my Daimler this year I went in the reverse direction and subdivided circuits because despite being a 1967 car it only has 2 fuses , of 50 and 35 amps ( blow rating ) ! I got some help from an ex Lucas engineer and had a very interesting talk with him about the subject . Apparently modern cars have so many fuses because the wiring now is very thin indeed and most wires will not carry in excess of c.7.5 amps without overheating. The old large capacity fuses were for large capacity wires , and apparently very rarely resulted in fires . The real merit of what I did, apparently, was that it preserves redundancy , in that if say the indicators blow, it doesn't blow everything else as well .

rah59 · Post by **rah59** » Mon Dec 31, 2012 4:44 pm

Hi all

old cables were oversized to restrict volt drop (VD) this is as a result of cable resistance,if the vd is excessive the heating effect on the cable may be beyond the capacity of the insulation. Early insulation was rubber and later PVC. Mordern cars with alternators operate at higher voltages (C15V) with modern insulation the volt drop os less of an issue, where the cable can operate at higher temperature further modern cars have management systems which monitor various functions it is thereforemore important to reduce the size of each circuit.

Robin

PeterCrespin · Post by **PeterCrespin** » Mon Dec 31, 2012 9:14 pm

Heuer wrote:
..no collapsible steering wheel..

FWIW S1.5 onwards have a collapsible steering setup, with both a mesh-type outer column and telescopic inner, constrained by shear pins.

Pete

Durango2k · Post by **Durango2k** » Mon Dec 31, 2012 9:45 pm

http://i55.tinypic.com/6y0580.jpg

Carsten

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