Fuse box Replacement

[NonMember]

2 hours ago, clive said:

Back to fuses. What I don't understand with our cars is why the 3? main brown wires off the solenoid are not fused to protect everything.

Because it wasn't the "done thing" back then.

I've seen it suggested that early fuses has a reputation as a weak spot. Certainly the number of electrical problems I've had that were caused by the crappy Lucas fuse box does seem to exceed the number that could have been mitigated by more fuses. If the MTBF of the protection is worse than the MTBF of the thing it protects, then it's not useful. And having had a full electrical failure (mercifully brief and self-recovering) while driving spiritedly at night in an 1850 Dolomite with overdrive... I'd much rather not have anything in there that increases the likelihood of such an event.

[Badwolf]

Thanks for that. Personally, I hate crimped connections but understand the reasons for them. These days, I usually pass the wire through the connector solder the front and crimp the back to get the best of all. I notice that the loom connectors appear to be soldered on my Spit as this (which proves your point) caused problems with my brake lights as the solder only partially caught the wire but melted the insulation. When the joint fractured, the cable was still held in the connector by the insulation so the problem was not immedistely visible.

[dougbgt6]

1 hour ago, NonMember said:

I've seen it suggested that early fuses has a reputation as a weak spot

Suggested?!! It's the worst designed thing on the car! The whole reason for changing to a blade box is that the existing thing is bound to repeatedly fail.

BW, I crimped all connections to the box, however the links between the red, purple and green groups are soldered, heavy single core copper wire wrapped around the base of each blade and soldered. A lorra, lorra solder! To have crimped it would have doubled the number of crimps required and put multiple connections to the blades which I think is a worse solution. 

I put my box on so that the cover opened from the left, which is I think is up side down. I did this for for ease of connecting to the loom. The connectors are at one end of the box, the other end holds the spare fuses. There's not much movement on the loom and the connectors line up when the box is upside down.

I never thought about the LEDs (despite having once been a member of the IERE  and my initials are LEDB )  The wired together blades are on the top, (which is the bottom ) However, when a fuse blew the LED came on, so I don't know what's going on there, maybe I got it right by accident). I rely on my fuse diagram for error finding rather the LEDs which could be misleading. The red group only has power when the side/main lights are on, the green group only when the ignition on. Only the purple group has power all the time. So a fuse could be blown, but with no power the LED won't come on.

Doug

 

 

[Colin Lindsay]

55 minutes ago, dougbgt6 said:

Suggested?!! It's the worst designed thing on the car! The whole reason for changing to a blade box is that the existing thing is bound to repeatedly fail.

I haven't replaced fuses in the GT6's original 3-fuse box since about 2005... nothing ever seems to blow, short or otherwise give bother.

[dougbgt6]

Maybe the mk1 has a better box?

On my old mk3 box the two "spigots" (?) at either end of the fuse are not connected till the fuse goes in. They are not sprung against each other and grip the fuse poorly. They Inevitably sag and one or more of the 4 no longer connects. The solution is to pinch them together which tends to open up the locating holes and makes failure happen all the more often.

Alternatively you are Mr Lucky (as well as Mr Smug, see bottle jack thread )

Doug

[Clive]

2 hours ago, NonMember said:

Because it wasn't the "done thing" back then.

I've seen it suggested that early fuses has a reputation as a weak spot. Certainly the number of electrical problems I've had that were caused by the crappy Lucas fuse box does seem to exceed the number that could have been mitigated by more fuses. If the MTBF of the protection is worse than the MTBF of the thing it protects, then it's not useful. And having had a full electrical failure (mercifully brief and self-recovering) while driving spiritedly at night in an 1850 Dolomite with overdrive... I'd much rather not have anything in there that increases the likelihood of such an event.

But it is the done thing these days. If the brown wires were protected by fuses I would have got my spitfire to spa as a repair would have been much easier rather than incinerating a sizeable bunch of cables. 

Using a "battery terminal distribution box" from a modern car offers basic 50 and 100amp protection, and chances are the fuses will melt before horrendous damage occurs in the event if a dead short. In fact I ought to take a reading of the cable resistances to see just how big a fault current could flow. At a guess 1000A which should melt a fuse very fast.

But I am happy with my new setup, it just needs labelling and live testing. A job for Saturday... Fingers crossed my alternator has survived.

Totally agree with Doug. The Lucas fusebox is just a dreadful design, doomed to fail as it gets progressively worse with use ( contacts get worse from corrosion, heat melts the box a bit, less tension on fuseholder....contacts get worse etc etc) The Nissan fusebox used today in some commercial plant is far superior but uses the same cheers, and is used as it just keeps working.)

[Badwolf]

Doug - Tested the leds on this particular fuse box and they work either way around so there is no problem of reversing the po!arity (older Doctor Who fans take note).

[Colin Lindsay]

1 hour ago, dougbgt6 said:

Alternatively you are Mr Lucky (as well as Mr Smug, see bottle jack thread )

Doug

Not to mention: 'Mr Elephant' on the 'other' forum....

[Badwolf]

Doug/Aidan - What gauge wire did you usd to link the input side connections of the new boxes. Was it single or multi strand (Doug, just noticed you used single strand)

[Clive]

You wouldn't use single strand in a car, too prone to breakage.

[AidanT]

Used a thick single strand CSA of 4mm sq. I would agree with Colin normally but this is in a static non flexing position so pretty safe not to fracture

 

Aidan

[dougbgt6]

You got me worried now Clive! I shall not sleep well tonight! Actually, I have dreamt about other threads on here, I'm spending too much time on line

"Too prone to breakage" Well, the fuse block blades are in an encapsulated block, close together, all you can be worried about is vibration, can't see that's gonna be a problem.

It was out a 30 amp mains cable, bought for an electric shower (certainly not now Kosher ) 

Doug

[Clive]

Sorry, I think I have misunderstood. using a solid piece of copper to link fuses (create a busbar) should be fine within the fusebox. But external to where movement may occur would be a bad move. So I think you are all safe....

Years ago I converted my vitesse, plus a couple of other friends cars, to alternators by using a bit of copper pipe cut open and flattened in a vice, then cut tabs for the various spade connectors that needed joining, Very simple way of creating a busbar without altering a loom. Just don't directly bolt it to the car. 

[SpitFire6]

Hi,

 Nice thread.

I would not use solid to bridge contacts. Stranded every time.

• Less "heat" needed to solder. Less chance of heat damage if pre-tinned in situ.
• You will find some in your house.
• It might be tinned; faster soldering.
• Very flexible. Very easy to bend around contacts.
• Better resistance contact.
• Can be made rigid with solder.

Never understood PVC insulated solid copper wire. Does it belong in the past like ring-mains?

Interested in other views.

Cheers,

Iain.

[dougbgt6]

13 hours ago, Spitfire6 said:

Never understood PVC insulated solid copper wire. Does it belong in the past like ring-mains?

Ring mains are in the past?!! I shall start stripping mine out after lunch and replace it with...……………?

db

[dave.vitesse]

When training I was taught where there is vibration always used stranded wire as solid can fracture under such conditions. Though maybe not a large busbar.

Fuse fracture wasn't uncommon, that's why the headlights and lots of other stuff wasn't fused years ago. Using a fuse for each light would have reduced the risk, but that would have increased the costs and complexity. I got the impression a car electrical system was kept as simple as possible.

The solid wire is said to have a higher current rating for the same overall diameter than the stranded and will bend, then stay where its put. Hmm- I think the former has more to do with cost.

I had to do loads of maths in the past to prove cases, but have always believed the practical applied theory and experience had much greater value. Which does come out in most of the threads on the Forum.

Just my ramblings.

Dave 

[Anglefire]

Thanks Clive you have reminded me the reason!

the lack of fuses on the lights I think was due to the poor quality fuses back in the day - though why having a fire under the dash is better than the lights going out is one for the philosophers to discuss 😂 

and I would have thought that in the 70’s they would be ok. Well at least for the warranty period anyway as they do lack a certain something compared to modern fuse boxes. 

I have one to fit in mine when I get some time. 

 

[Anglefire]

Sorry I posted before I saw the multitude of replies since Clive’s original one 🤷‍♂️

[dave.vitesse]

The Herald/GT6/Spit/Vitesse electrical system goes back to the 1930's with some changes to connectors and gauges. I have my late Father's pre-war training notes on these systems and can remember asking him "Why so few fuses" and he said. They didn't trust fuses.

Dave

[Badwolf]

Just about to start the job, when I will move over to my own restoration thread with my version (how to do it wrong!!).  However, before I do start can I just clear up the wire needed for the fuse box interconnects (bus-bars). The general advice is to use 4mm stranded wire.  Silly question, are 2 x 2mm wires twisted together as good, or running even 2 x 2mm on either side of the terminals?  I suppose there are horrendous calculations about amps, resistance, heat transfer etc... also....  I don't have any 4mm cable handy but have a stack of 2mm. There is always domestic flex, but I don't think that I have anything heavy duty enough. Over to the sparkies on the team.

[NonMember]

Err... 2*2mm is not equivalent to 1*4mm. It's the area that matters, so you'd need 4*2mm.

That said, what diameter are you measuring? 4mm diameter of copper is a BIG cable, good for 100A over a few metres. A single 2mm cable will do 25A, more over very short distances, which would cover your bus-bar needs if the incoming feed is to the centre.

[SpitFire6]

Hi,

 never known anybody use wire diameter for conductors. Americans excluded.

2 x 2mm CSA is better than 1 x 4mm CSA. More so at AC.

Cheers,

Iain.

[SpitFire6]

6 hours ago, dougbgt6 said:

Ring mains are in the past?!! I shall start stripping mine out after lunch and replace it with...……………?

db

Radial with a few more MCB's. ELCB's are a better choice though.

Ring-mains are a British and colonies thing. Served its purpose after WW2.

Radial mains are allowed & better IMHO.

Cheers,

Iain.

 

[Badwolf]

Ok gents. So, you are dealing with a man with a soldering iron, crimp pliers, the fuse box mentioned earlier, the original 3 wires with 12v coming to the box, 10 wires going out and the need to connect 4 blades for one wire coming in, and three blades for each of the other two coming in. Do I take it that 2mm (25amp) will be sufficient to take the load using it as a 'bus-bar' connecting the blades of the fuse-box over a length of no more that 3 inches, power into the center blade on the blocks of three, and off center (blade/power/blade/blade) in the block of four. If not, what do I need for safety.

23 hours ago, AidanT said:

Used a thick single strand CSA of 4mm sq. I would agree with Colin normally but this is in a static non flexing position so pretty safe not to fracture

The enquiries before were based on trying to make sense of some of the previous posting, total confusion now reigns... yes, it shows doesn't it!! I assumed that the 4mm in Aidan's post was the wire diameter, obviously now I know its the area.

[SpitFire6]

Hi,

 the more turns the better. There will be space to do this with 2mm CSA.

Cheers,

Iain.