11 replies to this topic

[Benito_S6]

Currently undergoing a winter restoration of my mini and have got the wiring loom out so looking into repairing, adapting and upgrading parts. One thing I have seen is converting the glass fuses to blade fuses. So after a few nights of searching and trying to work out what best way is to do this and as I haven’t found a definitive answer or guide, thought I’d post what I think so far and see if anyone has advice on it and if my thoughts are correct please.

Looked through crimping three wires together into one connector, piggy back connectors, going down to one larger gauge of wire and various other ways of getting round the issue of one input wire and three outputs. I’ve decided that maybe the best way of having multiple inputs is using a daisy chain technique I found on here (irostoke’s post and wiredbywilson). Then having the individual wires on the output side of the box. This makes it so each circuit is fused separately and makes for easy diagnosis I think. Would this be a safe and correct way of doing the wiring for the fuse box?

As for fuses, half the value of the glass fuse for a blade fuse. Other ways I’ve seen is 60% and 62%. Due to this being the main and most important part of the conversion I think it needs to be done proper. The original fuses are:
35 Amp
25 Amp
25 Amp
15 Amp

Obviously I’ve seen various recommendations for what the blade fuses must be. 35 Amp —— 17.5 Amp but this doesn’t exist so go down to 15? I’ve seen it on here that a 20 Amp would be more suitable so which would be best. Along with 25 Amp —— 12.5 Amp so go down to 10 but I’ve seen that 20 maybe more suitable. So, as I can find the options are:
35 Amp —— 15 Amp or 20 Amp
25 Amp —— 10 Amp or 15 Amp
15 Amp —— 7.5 Amp

I’ll mention wiredbywilson’s kit which is a brilliant product and I would buy but I hope to do this myself and learn from it. Whilst also helping others and not setting my mini on fire!
His kit uses the smaller amp fuses (15 Amp, 10 Amp and 7.5 Amp) so I am tempted to follow suit as I understand lower fuse would give more protection but finding contradicting answers has made me want to clarify exactly what the blade fuse ratings should be.

I know this has been asked before and the gurus are probably sick of answering this but I think it’s important to get this right and help others with it too as none of us want to be burning minis down do we!

I’ve attached a couple of pics. One is a diagram of how I think the conversion would be layed out along with a diagram of the connections on my fuse box and the other is a picture of the connections before I removed the fuse box.

Hopefully this isn’t too much waffle and it may help understanding of this conversion. Essentially the question is, would wiring up the fuse box the way shown in my diagram work and is it correct and safe? And, what actually are the blade fuse ratings that need to be used to be safe equivalents to the glass types.

Attached Files

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•  A6069E9E-4823-403E-9C23-ED32B4D61194.jpeg   66.28K   17 downloads

[DamoMini]

I am thinking of replacing the old fuses with blades as well and have been fixing the wiring installed by the previous owner.  I think you should have the wiring diagram of your car nearby while you sketch out your prototype circuit to make sure you understand which wires are feeding voltage into the terminals.  For example, according to the wiring diagram for my car (1978 Mini 1000), only one of the two brown wires entering the left side of the fuse box is actually carrying battery voltage (the one coming from the solenoid).  The other is taking power away from that terminal to the lights and hazard lights.  If you separate these in the new setup then the lights / hazard light circuit will no longer receive any power.  Probably should check the other circuits as well against the wiring diagram.

 

Looking forward to seeing how this goes!

[GraemeC]

You need to be carful splitting your fuses this way as you’ve actually increased the current that could potentially be drawn on a wire.

Take the white ignition feed at the top. Previously protected by a 35 A glass fuse (which is a 17A continuous rating).
You’ve halved this for the blade fuse, but then doubled up on the number of circuits being fed at that rating ie you now have a potential to draw up to 2x 15A continuous before any fuse would blow, so 30A continuous on the incoming white wire.

[jaysmini1983]

Take a look below,if you scroll down the page and click the picture. you can buy a kit over here and you can clearly see how its been done. 

 

https://www.wiredbyw...roducts-prices/

 

i have done this with no issues 

Edited by jaysmini1983, 14 November 2019 - 12:51 PM.

[Benito_S6]

Should of said that I’ve got a 1986 Mini Mayfair.

Yeah see what you’re saying Damo. Having checked the brown wire I’ve found that it runs back to the lighting switch so by splitting that side you’re right saying that would no longer get power.

Read what you’ve said a few times Graeme and I think I get my head round what you’re saying. Although I’m not sure there would be double the amount of circuits but I’ll look into that.

I sat and drew up a 8 blade diagram, splitting all the circuits on the right side into separate wires and followed the wiring diagram to see what goes where. This made it easy to see what wire does what and whether it would be worth splitting them onto separate fuses for the sake of fusing one wire on its own.

Having looked at it I don’t think it’s worth going to the hassle of splitting the purple wires into two connectors and having the brake test switch on one fuse on its own. Not having the stop light switch on its own. I don’t think there’s much benefit from having these separate rather than in one connector as they are now.

So I’ve then drew up a 4 fuse diagram. This would mean I wouldn’t need to add wiring on the left side of the box. On the right side, keeping the green wires in one connector and purple wires in one connector. However as the 3 light green and orange wires are already in two connectors and I don’t want to crimp them all into one, I’m planning to have the Rev counter and wiper motor on one connector, and the wiper and heater switch in another. Then putting this onto a 2 to 1 connector and having one wire run to the fuse box from that. This wire would then be the only one I’d need to add in.

As said, I’ve looked at wiredbywilson’s kit and that’s where I’m getting some ideas from. But I do want to build it myself.

Hopefully this explanation and diagrams are understandable and someone can let me know whether the 4 blade diagram that I’ve drew up would be a good way of doing it.

Cheers

Attached Files

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Edited by Benito_S6, 14 November 2019 - 04:57 PM.

[GraemeC]

OK, I’ll try and explain better.

Imagine you simply replaced the glass fuses with blades but kept the wiring of the 4 way box, and you used a 15A for the top fuse.
The white ignition feed will never have more than a 15A load otherwise the fuse will blow. So a TOTAL of 15A could be drawn by the two green wires combined.
Now split those two green wires so they have a 15A fuse each as in your 8 way box example. In theory the white wire could now be loaded with up to 30A without a fuse blowing (15A + 15A).

But we’d need to assume that the current carrying capacity of the white wire is around 17A as this is the continuous rating of the original glass fuse (it’s probably more likely a 20A cable to allow some safety). So in you 8 way scenario you could easily overload that cable.

[Benito_S6]

Ah ok Graeme thanks for that. I understand what your saying now. But with the white wire being the power wire it would only get the power from ignition switch through it? Not power from both the green wires flowing back into it, as it’s technically the supply. Regardless I get what you’re saying about the possibility of overloading so thanks for your help with that.

Could you (or anyone else) confirm if the 4 fuse diagram would be good to use as I think the only difference really from original is adding the one wire to reduce the two green/Orange wires down to connect to the one terminal on the fuse box. And obviously still need to find the correct blade fuse ratings which I think I’m going to use the same ones that wired by Wilson has used.

[GraemeC]

The device being supplied with power will ‘demand’ - ie power is ‘pulled’ down the wire rather than ‘pushed’.
Voltage will always be 12V(ish) but current will vary dependant on load.

For instance a 60W bulb will draw 5A where as a 5W will draw less than 0.5A. Both will work with thin wire, but the 60W bulb will heat up that wire and potentially burn it out.

The 4 way diagram should work fine. Just consider where you have joined to wires into one that the one wire may need to be a bigger wire for a similar reason to the fuse scenario - that one piece of wire carries all the current of the two joined onto it. If it is a similar size to the wire supplying the fuse then you shouldn’t go far wrong.

[Benito_S6]

Yeah I get about the current varying with load and realise now about the power being pulled into and through the white wire. After typing I remembered which way power flows.

Also in terms of that wire I was planning on trying to match it will the other side. Otherwise I’ll just have to find how many amps the circuit draws and gauge it accordingly.

Thanks again for your help, got there int end ey! Hopefully these explanations will help others wanting to do this conversion themselves.

I’ll be adapting my wiring soon but probably not installing till next year. Will take photos of how it’s done and let you know how it goes. May start a build thread to so will link this.

Cheers

Edited by Benito_S6, 14 November 2019 - 11:16 PM.

[Ethel]

Graeme's right. Imagine they're foot bridges for people rather than wires with amps. If there's two green bridges that'll take 15 people each and one white bridge supplying them it'll have to be able to support 30 people at a time to keep up when both green bridges are at full capacity.

Since the white (ignition live) is going through a relatively expensive and fragile ignition switch you could solve both problems by using a relay to switch a chunky enough permanent live direct from the solenoid.
It also makes good sense to run the ignition coil direct from the ignition switch and without a fuse to minimise the component count: suddenly loosing engine power could easily be more disastrous than melting some wiring, and if you're behind the wheel you'll hopefully have the option to turn the key. Just be cleverer than Rover and don't bundle your unfused wire in with the fused ones where it can melt the lot.

[Benito_S6]

Ok thanks again. I did understand but that’s made it very simple. I get about the fact the wire can be overloaded but the white wire has the two green wires feeding into it any way from the factory. That isn’t something I would be changing by taking the two wires out of one shared connector and putting them into their own.

To be honest though after thinking about this, how much benefit is there really when changing to blade fuses. Providing the old glass fuses are new and the fuse box has no corrosion and good connections what’s the point in changing. The original fuse box works fine and is proven from factory and many years of working so I think I might just remove the risk and hassle and stick with it. Maybe.

Thanks for all your help though and hopefully this can be helpful to others aswell.

Cheers

Edited by Benito_S6, 15 November 2019 - 12:47 PM.

[Ethel]

It's the other way round, though what we call +ve or -ve is largely academic. It does matter in as much the unfused whites feeding the greens on the other side of the fuse can be feeding unfused circuits too - such as the ignition.