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PostPosted: October 5, 2017, 9:19 am 
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Hey all, how does this look? Does it make sense? Fuse size recommendations?

(The little stars are dash switches)

I drew this up using a high tech method called 'Microsoft Paint'.

This does obviously not include a lighting circuit.

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PostPosted: October 5, 2017, 12:18 pm 
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I assume that you are going to add some sort of thermo-switch in the control line for the E fan? If wired as shown the battery will just run down.

You might think about some sort of fusible link for battery wires.

Other than that, so far, so good IMO. :cheers:

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PostPosted: October 5, 2017, 12:30 pm 
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Well the Efan has a manual switch, that's what that star is and then that's what controls the relay. How would that run down the battery?
(Unless you forget to turn the fan off)

All the circuits go through the fuse box, what do mean fuseable link?


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PostPosted: October 5, 2017, 1:47 pm 
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In over 40 years of working in electronics and being a shadetree mechanic dealing with automotive wiring, I've never seen a switch drawn as a star in any schematics I have run across. I interpreted it as a terminal block. It made sense to me with regards to the fuel pump circuit. I just assumed that was the case for the Efan

If you have a switch, then never mind.

As for fusible links, there is a lot of energy that can be delivered from a battery if that cable shorts to the chassis. A fault like that could allow thousands of amps. A fusible link, like a fuse, allows the normal high current to flow but protect against catastrophic faults in the main power cable. as close to the battery as reasonably possible for the best protection. An alternator, even if the control system fails, is current limited by design. Fusible links are Fuses but generally in very high current ratings. If your fuse box has a single 200+ amp fuse, then it may function as a fusible link. It your fuse box has only5, 10, 20 and /or 30A fuses, then modern systems would have a fusible link located elsewhere.

My 1956 MGA had no fusible link and it had only 2 fuses, one for the horn, one for a few other circuits. Some circuits had no fuse at all. Burnt wiring is common in old British cars. Modern vehicles are much better protected against faults. Some cars today you will see fusible links mounted right to the battery terminal. I wouldn't intentionally wire a car without main fusible link. YMMV.

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PostPosted: October 5, 2017, 2:17 pm 
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Right! That's why I'm my original post I said that the stars are switches, to try and avoid confusion.


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PostPosted: October 6, 2017, 9:11 am 
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So I ended up getting a fuseable link off ebay per your suggestion:

Image

It's out of a newer Acura.


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PostPosted: October 6, 2017, 12:00 pm 
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Cool. If everything goes well, you'll never know it is there.

Only in the event of a catastrophic short will be thankful you have it. :mrgreen:

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PostPosted: October 9, 2017, 9:50 am 
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Where would one ideally place an ammeter in the original image?


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PostPosted: October 9, 2017, 1:44 pm 
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Generally everything except the starter motor should go thru the ammeter.

I think you need to break down a bit and either start going for multiple pages or make the things smaller in your diagram. The symbol for a switch is simpler than your star and that's an easy change. It's convention to try to draw the diagram with inputs and sources on the left and outputs towards the right. It helps apply some organization to the drawing and makes it easier to read. Things flow left to right. So the battery should be on the left side and the ground on the left side of the battery. This will also help reduce the number of times that lines cross each other so that helps make it easier to follow too. It will also organize your thoughts bit. It's worth doig all this because someday you will want to know what some wire does and eventually writting or noting the colors etc. will be a help.

You probably don't want to run your whole electrical system thru the ignition switch. Headlights, for instance, draw a lot of power and they might over whelm your ignition switch. LED headlights less so though. I don't know the rating of your ignition switch. You can buy a big master switch and that would make sense for a home made car. They are required on competition cars and common on boats so they are not hard to get and could give you some peace of mind.

Be conservative with the ratings of the parts you use. If your ignition switch says "20A", deciding on an average current of 19A is really pushing it. Others here would have a good opinion of how close to approach ratings.

Your connections should be made with good quality crimps and new hardware. The goal is "gas tight" for your connections. A crimp will actually cause the metal to flow and become almost one piece of done properly. If you connect a wire with a grommet onto a post, for instance the main power switch, you should use a new star washer that has sharp edges and will cut into the metal a bit - making a gas tight seal again. When you put that fusible link on the battery you should land up with clean bare metal connection, so try not to keep putting it on and taking it off. You can clean the terminal with a metal brush.

A simple wiring system is a great goal!

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PostPosted: October 9, 2017, 2:25 pm 
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Great info. Thankyou. This was drawn up on paint hence the stars for switches. I drew it to make more sense to me I guess, with the general layout pretty much matching the physical layout of the components, more to make it easier for me I guess. I'll definitely start looking at my amperage ratings. Thanks again for the great information.


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PostPosted: October 11, 2017, 5:57 am 
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Fuseable link:

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