Classic cars forum & vehicle restoration.

1stpop · Joined: 03 Dec 2007 Posts: 109

I am just about to re-wire my 1947 Morris 8 and after adding an alternator I will be getting rid of the old control box (its had it!). This originally contained two fuses for the two main feeds - constant/ignition feed. When I add a new fuse box wheres the best place to intordue it? In the feeds or after the switches? I was thinking of adding a fuse for each seperate thing e.g. main beam, side lights, traffictors, brake lights - you get the idea.

Would appreciate any thoughts on this

thanks

PAUL BEAUMONT · Joined: 27 Nov 2007 Posts: 1281 Location: Barnsley S. Yorks

I'm sure ukdave2002 will comment on this, but my understanding is that there are 2 schools of thought on this topic. If you put fuses in the feeds you use less fuses because one feed may well supply several functions. This was the classic solution, probably driven by cost. The down side is that you need biggish fuses - typically 35A which need a massive short to blow them and when one blows you lose lots of functions.
Alternatively you install fuses after the switches and use a fuse to control one or 2 functions. This way you use more fuses but you can protect each circuit individually with a fuse more suited to the load. That way, if your radio for eg develops a short it doesn't take the wipers out on a dark wet night!! Most (all??) modern vehicles use the latter system for the obvious reasons.
Choice is really yours Originality v Usefulness probably driven by how much you will use the car and if you are a concours award hunter!
PAUL

ukdave2002 · Joined: 23 Nov 2007 Posts: 4105 Location: South Cheshire

Hi, as you say the Morris has 2 fuses, 1 feeds things that are only live when the ignition is on, and the other ignition fed.

As you are starting from scratch I would add a few more to fuse things individually.

Dave

1stpop · Joined: 03 Dec 2007 Posts: 109

the two main fuses wont be there anymore beause the control box will be removed - so I will plae the fuses after the switches in each circuit - thanks for the advice

1stpop · Joined: 03 Dec 2007 Posts: 109

How can I find out the right fuse size for each piece of kit e.g. lights etc?

Is there a standard list of fuse sizes?

Phil - Nottingham · Joined: 01 Jan 2008 Posts: 1252 Location: Nottingham

Add up the wattage taken and divide by 12v, round up to next size. If it is a motor try 15a or 25a
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