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Wiring Remote Switches


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#1 paulrockliffe

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Posted 03 January 2018 - 02:41 PM

I'm planning to move my switches to a box mounted between my seats as I can't reach them when strapped in because of the harness, but also because the seats end up further back in a Minus.

I've started accumulating the bits I need and have a question about fuses.

To wire to the box I have a length of multi-core that has 1 x 25A wire and 9 X 16.5A, this is much neater than running two random wires per switch.

I'm really wondering whether I can use the 25A as a switched-live for all the switches so I can get away with running just one length of cable - it's really in the cabin so don't want too many cables.

If I can I would need to move the fuses as well, is that right? I don't think I want a single point of failure for each switch.

Switches are:
Fuel pump - continuous use, but can be wired direct to the boot.
Starter - the starter acts as a relay so low current?
Lights - will be rewired using relays
Ignition switch - what's the current draw?
Camera switch - turns on the screen for a rear-view camera.
Hazards
Heater fan - current draw?
Fog lights - LED so low current.

Does that sound like something a 25A supply will cope with? I can bring a larger supply directly from the battery if necessary.

Any other thoughts or advice?

Thanks.

#2 paulrockliffe

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Posted 03 January 2018 - 02:42 PM

Sorry, website said there was a posting error, can a mod kill the duplicates please!

#3 Icey

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Posted 03 January 2018 - 04:56 PM

So a question that should be considered - why don't OEMs tend to use multi-core?

 

The answer invariable is because it's a pain. It's harder to shape around panels and if one wire goes bad you need to throw away the whole thing.

 

If you are after neatness, just bind the wires with a non-adhesive tape.

 

 

However, if this is just to drive some relays and tell-tale lights I don't see much of a problem. I'd build the thing with a very low current draw in mind (i.e. no load run through the switches). You'll have some work to do to convert everything to relays but it can be done without to much bother (all of my stuff is, but hazards are your biggest challenge as discussed on here before).



#4 paulrockliffe

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Posted 03 January 2018 - 05:40 PM

Thanks, there's no issues running multi-core, it's a straight run up behind the dashboard where it'll tie into the existing wiring and it's such a short run that if there was ever a problem with it it would be a quick job to replace the whole thing. I doesn't make sense for OEM, but the car is miles away from what would come out of a factory.

Does everything need to be on relays? I'm pretty sure the hazards don't, the wiring is 16A and all the switches are 40A or more, so I was planning to only add relays for the headlights.

#5 Icey

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Posted 03 January 2018 - 06:34 PM

Does everything need to be on relays? I'm pretty sure the hazards don't, the wiring is 16A and all the switches are 40A or more, so I was planning to only add relays for the headlights.


Technically, no, but hazards specifically arent just a couple of poles. Remember they turn off the indicator circuits as well as turning on the hazard circuit.

If you put everything through relays then your idea of having a single input with multiple outs will be a lot easier to execute as you can keep the complex (for a Mini) parts behind the dash.

#6 KernowCooper

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Posted 03 January 2018 - 09:40 PM

FAQs Electrical has all the normal current loads per circuit if that helps



#7 Compdoc

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Posted 03 January 2018 - 09:41 PM

If you are just moving a switch panel and extending the wiring, why not not order a metre of each correct colour and extend each one including all the various power wires.

http://www.vehicle-w...thin-wall-cable



#8 paulrockliffe

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Posted 04 January 2018 - 01:27 PM

FAQs Electrical has all the normal current loads per circuit if that helps

Thanks, that should be really useful.



#9 paulrockliffe

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Posted 04 January 2018 - 01:31 PM

If you are just moving a switch panel and extending the wiring, why not not order a metre of each correct colour and extend each one including all the various power wires.

http://www.vehicle-w...thin-wall-cable

 

That's still an option, the disadvantage is that it would need more than 10 wires, so two runs of cable rather than one.  Not a huge deal, but most of the wiring in my car is non-standard so I suspect when I get the dash off there's a lot of tidying up to do and that'll be simpler if I'm not splicing into a mess of wires.



#10 MiniBGT

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Posted 05 January 2018 - 08:00 AM

Individual wires through convolute with appropriate fittings and secured with P-clips is neat.



#11 phillrulz

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Posted 05 January 2018 - 07:45 PM

I had a quick read of this got deep in how to do it ... then deleted it all give me a lill bit and ill try get my head round it.

 

 

I dont think i liked the limit of the 25A cable. 


Edited by phillrulz, 05 January 2018 - 07:46 PM.


#12 phillrulz

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Posted 05 January 2018 - 07:50 PM

Right.

 

That 25A cable isnt beefy enough.

 

Here's the good news tho. Just install a bank of relays and switch the relays using your buttons. That way its low current at your switch box and the high current it taken care of by the existing fuse board and cabling. 

 

Just use the 25A as the supply for all the switches that switch the relay coils then the other cores for the switched lives  

 

The safe way would be to fuse the 25A cable at supply and in theory fuse the individual supplies at the switches as you could send 25A down a 16.5A rated cable... So a small fuseboard inside your switch box actually helps distribute the voltage.  Or you could always fuse the 25A cable at below 16.5A as alot of people dont realize. Fuses and breakers are to protect the cabling not the device connected. 

 

 

Sorry im kinda a sparkie so i go overkill. Better to be safe then have a fire. 

 

 

Infact i believe there is a trader on here that does relay banks... Lets see if i can find them 

 

Wired By Wilson, thought he did relay banks, but cant see it. Im sure he'll be happy to help build one if you do struggle. 


Edited by phillrulz, 05 January 2018 - 08:06 PM.


#13 paulrockliffe

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Posted 05 January 2018 - 09:50 PM

Hello Phil,

Thanks for that, I will should be useful. I presume that none of the individual components are problematic on their 16A wires from the switch (except perhaps the lights, but they can be ignored as they're definitely going on relays), but it's them all sharing the common 25A supply that is the problem?

If that's the case is there a sensible hybrid approach you would be happy with? eg I can't see it makes sense to put hazards on a relay. If most of the risk was from, say the heater pulling high current, then just putting that on a relay could leave everything else OK?

I'm happy wiring up whatever method, but I guess I'm averse to relays unless they're really necessary because they're more wires, and more connectors and a bit more faff. All they really do is reduce the current at the switch, there's still high current somewhere, but the switches are 40A or something. But at the same time it needs to be done safely.

If it's purely down to the 25A coming in, I can bring an xx amp cable directly from the battery, it's a 50cm run, and there's already a run through the car in 10mm to the starter solenoid to follow, low.

Possibly I could fit a master switch to the existing run to create a switched and unswitched live at that point anyway?

I was aware of the fuses protecting the wires rather than the components, reminding me of that makes me wonder why there isn't any fuse on the main cable to the starter solenoid?

#14 phillrulz

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Posted 06 January 2018 - 12:26 AM

Yea, no individual component has issues. The starter solenoid is a little close however its only on start up. Fuel pump insnt too bad so long as its good cable. 

 

Personally i wouldn't touch the main live feed wire from the battery as its high current and you dont want any resistance when your pumping over 200A (or trying to if resistance is too high).Reason why they dont fuse the main live from the battery is due to the sheer amount of current required to run the starter motor. Car battery have a Cold Crank Amps (CCA) rating in the hundreds of amps you'd have to replace the fuse every few starts of the car. Just look at when you jump start a car, the leads get hot in less than a second. 

 

Just checking the electrical FAQ as suggested by KernowCooper 

 

  • Fuel pump - J reg i guess could be SPI? Injection fuel pump 10A
  • Starter - Presume you mean solenoid 10-12A   <--- personally that seems a bit high especially for the ignition switch unless its relay assisted which it wouldn't be in my car
  • Lights - You said will be done on a relay so say 0.5A for relays
  • Ignition switch - Ignition coil 4A (unsure of your wiring but my older mini the ignition switch also feeds things like wipers 1.5-9A(stall) ) 
  • Camera switch - unsure of specs doubt its over 1A
  • Hazard flasher -  7A
  • Heater- fan high speed 10A
  • Foglights - lights presume you mean red rear foglight LED - 0.5A

 

Total 54A . 

Worse case scenario.

 

 

So yea an amalgamation of relays and normal switches to break the load up a bit. Unless you want to run a feed from the starter solenoid to a new fuseboard then switch it that way. 


Edited by phillrulz, 06 January 2018 - 12:39 AM.


#15 paulrockliffe

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Posted 06 January 2018 - 11:10 AM

Thanks, I should really have looked at the link, it was on my to-do list.

The car is a Mini Minus and although it's based on some mini loom or other it's been modified quite a bit, with fuses wired to under the dash on the passenger side, so I doubt it really matches up to any particular car.

The fuel pump is a facet one, not a standard item. I'd have to check but I'm pretty sure it's wired with a fuse box that's switched and another that isn't, with everything hung off those, rather than having anything else running through the ignition switch. If there is anything on the ignition switch directly, I'll move that

The fog lights are a set of LED lights on the front, but the draw will be similar.

Your worst case is pretty much never going to happen, but I can see how it's possible to easily get 25A through. I guessed the heater would be the most likely to cause problems and it looks like that would be the obvious candidate for a separate supply.

I think I have enough to go on now, I think the best bet is going to be a new supply from the battery to a fuse box behind the seats, but I might modify that as appropriate depending on the specifics of each circuit.




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