Fuse Box - Spitfire MKIV

[NevSpit]

Hi all,

Can anyone advise how you actually dismantle the fuse box in a Spitfire? I want to disconnect the wires from the glove box side, clean up and replace. At present some of the circuits only seem to work if you hold the wires at a certain angle...

Many thanks.

Paul.

[Pete Lewis]

some of these are a hard solder/welded connection of the feed harness so without ...what have you got,  its hard to give a clue

 

the main problem with the simple fuse boxes is the two sprung blades that hold/connect the fuse cap actually use the fuse cap to connect the two blades together  any corrosion or poor contact to the fuse cap will render certain circuits dead even though the fuse is intact, as its not using the fuse to make the connection

 

Pete

[Mjit]

Buy a new fuse box/foam gasket now, as in my experience something will break or you'll find something that means you want to replace the current one anyway.

 

There should be enough slack in the wire loom to let you 'pop' the fusebox out of the bulkhead and in to the engine bay, which makes access a lot easier.  The box is held to the bulkhead by, from memory 4 plastic tabs on the back/inside car side of the box.  In theory you squeeze these together and it just pops out.  In my experience this sort of works but at least 1 of the tab will have gone brittle and just snap (new fuse box required #1).

 

The wires terminate in special plugs that slot in to the fuse box, each one forming a single blade and 4 of them (2 each side) forming the contacts that grip the metal ends of the fuse.  With the box in the engine bay you can see what you're doing and find the little 'tang' that holds each blade/plug in to the box and release them.  Now if nothing broke releasing the fuse box from the bulkhead sod's law states one of the tangs will break at this point (new fuse box required #2).

 

With the contacts out you can clean them up and inspect them and either re-insert in to the box (making sure they all go back to the same places) and re-insert the box in to the bulkhead.  If nothing's broken you'll probably find some overheating damage from some point in your car's past.  There was some melting of the plastic around one of the plug/blades in my box for example (new fuse box required #3).

 

 

If you do decide/need to go to a new fuse box but your plug/blades are in good condition you just need to feed the loom out of the old box and in to the new one, then plug all the blades in to the new box.  Mine hadn't weathered the years so well but there was plenty of slack in the loom to snip them off and fit the new ones (included with the new fuse box) in their place, then slot in as before.

[dougbgt6]

Mine's separated from the bulkhead and dangling at the moment, so yes, there's plenty of slack in the loom to work on the back of the fuse box. I intend to go a step further, rather than a direct replacement, a larger box with more fuses. 3 (on mine) is not enough! I'm going to split the wires out into separate circuits.

 

The head lights are famously not fused at all!  Also, all the current for the headlights goes through the switch. I've bought an addition loom (from China) with fuses and relays for the headlights but you might prefer to include headlamp fuses in a new fuse box.

 

http://www.ebay.co.uk/itm/H4-9003-Headlight-Booster-Wire-Harness-Connector-Relay-Fuse-Socket-/390938014554?pt=LH_DefaultDomain_3&hash=item5b05b8b35a

 

Suspiciously cheap, you couldn't buy one relay here for this price, but I bough it and it looks robust enough. I'm going to have to extend the battery feed and remove and replace the headlamp connectors to get them inside the headlamp cowling.

[AidanT]

All

 

Just reviving this thread as i am about to update my fuse box to a modern Spade type. i seen somewhere some pictures of Cookies work on this which i intend to follow as best as I can but it does not answer this.

 

There are some circuits that are just not fused and are linked to the live side of the fuse box, one of which is the ignition coil. I have lately rewired my coil with 1 mm thin wire which is rated to 16.5A but the question is for this and other similar circuits, what rating fuses have others used?  A list of the circuits and what rating you used would be really raised would be really useful

 

Aidan

[rlubikey]

Well, as the fuse is there to protect the wire, you should use something less than 16.5A. What does the coil take? 3-ohms (is that right?) across 14V is 4.7A (ign on, points closed but engine not turning), so try 10A.

 

Cheers, Richard

[AidanT]

That's what I thought tbh. Has anyone a list for the other circuits? The std triumph fuses must be way over what's really needed

[Clive]

Fuses are usually about 1.5 to 2x the expected rating,to allow for surges etc.

 

Does that help?

[AidanT]

Hi Clive. If I knew the expected rating on the circuits then yes. Unfortunately.....

 

Aidan

[Pete Lewis]

amps  =  volts 

              _______

               ohms

 

so need a meter to check the resistances 

[AidanT]

Thanks Pete that's one thing I can do

 

Never thought of it!

 

Aidan

[Pete Lewis]

Its one of those formula you get 54yrs ago in schooll and never use it till tonight

 

sad !!! Often use trig but never any exponential equations or algebra where they just cruel or what

back then

 

pete

[AidanT]

Remember it well! What's the square root of minus one again? Who cares!

 

Aidan

[dougbgt6]

Square root of -1 is

 

I

 

and all sorts can be proved by believing it! 

[Clive]

Doug, that i looks like a 1 !!

One of those things which really gets the old brain in a tiswas, but a very useful bodge! I don't think I am sad to have left that stuff behind 30 years ago.

 

anyway, more useful would be amps=watts/12

 

So, pair of headlights. 55w x2 =110watts

110/12 = 10 (near enough)

But here you need to factor in the extra sidelights and tails, another 20-30w (say 3A)

I would be using a 35A blowing fuse on that circuit.

[Pete Lewis]

When I went to school watts did steam engines

foorballs were leather half full of water

studs were nailed on and boots were Boots loads of dubin and mud

not the pansy things they wear these days , they have it too easy

exercise books and inkwells

if you blew down the gas pipe all the bunsons burners went out

then you got the cane ouch

 

but still remember i=v/r and tan = opp/adj 2=8/4 all stick with you

 

then simple algebra you can swap

and the old apprentice Zeus pocket book comes out

 

pete

[AidanT]

Well when I did applied Maths it was r and not i. probably to avoid that confusion!

 

As an accountant though I have never used it although I must say I have come across some imaginary accounting!!!!!

 

Aidan

[dougbgt6]

One of my daughters has a T shirt that says "Another day gone and still I haven't used Calculus"

[Dick Twitchen]

And to complete Pete's 'tan=opp/adj' I recall reciting 'silly old Henry caught a hairy toad one afternoon' endlessly.  Finally found it useful doing astro navigation, but that is really taking thread drift too far!

Dick

[dougbgt6]

Richard of York gained battles in vain.

 

Spot the error.