extra fuse box

Post by **sidsmith** » Mon Nov 20, 2006 7:32 pm

Hi there, I could do with some info' on electrics if some one can help me out. I have put an extra fuse box on the bulk head containing 4 extra fuses so that i can run spots, radio, etc.Bearing in mind my car is a 1956 splitscreen that I have converted to Negative Earth , How/ where can I run a wire from that can go to the extra fuse box and become live when I turn the ignition on. I can't take the power from the solenoid as there isn't one , and I can't get to the ignition (key ) switch. Ideally if it could be connected somewhere on the bulk head that would be great. Your comments would be most appreciated.
cheers sid
(yes I know that i'll probably need to convert to an alternator at sometime)

Post by **Rob_Jennings** » Mon Nov 20, 2006 8:07 pm

i was about to do this on my car before it had to go to the garage for some serious welding!

my plan was to take a feed from the brown wires where the regulator would have been (alternator and neg earth means no regulator on mine) or from the battery, through a relay that is energised from the white wires at the fuse box (switched from ignition). The reason being that the key really should not be presented with a lot more load than it already has. The relay will come on with the ignition and thus all the fused accesories. If you wanted perminant feeds then they could be in the same fuse box direct from the battery.

was going to write up a wiki page when i was done, but may draft something before now

Post by **Alec** » Tue Nov 21, 2006 6:59 am

Hello SS,

you can as Rob says have a single relay, controlled by the ignition switch but I would feed the fuse block directly from the battery or starter switch whichever is easier. (Ensure that you use a large enough cable.) I would then use seperate relays for each function that you feed from the fuses. (You may want to make an exception for the radio, as it is low power and the benefit is that you can listen to it with the ignition off.) Bear in mind that your spotlights need to be controlled by the high beam as they should not be capable of being on when you are on dip so a relay(s) is beneficial there.
I know my version is more complicated and expensive but if a relay fails, only one function will be affected.

Alec

Alec

Post by **sidsmith** » Tue Nov 21, 2006 6:49 pm

hi there, at the moment with the new fuse box connected , I was running a temperature gauge from it , but I have found that the temp' gauge was permanently live which mean't the battery was going flat, so i have disconnected the temp' gauge from the fuse box. the only reason I was using the fuse box was because I had to put a negative earth voltage stabiliser on the car so that I could put a temperature gauge on. So being completely ignorant of electrics (i'm trying to learn ) I could really do with a simply explained way of doing it. By the way I still have the old loom on the car which means i can't see what colour the different wires are.
sid

Post by **Rob_Jennings** » Tue Nov 21, 2006 7:16 pm

ok, im not sure exactly how simple I need to be on this, so don't take it too personally if it sounds a bit dumb.

Get a automotive relay from a car bits shop or electronics shop. These have labled connection for the coil (the bit that makes it work) and the contact (the switch bits). Make sure the coil is 12v rated, and the contacts should be rated 30 Amps or higher.

Mount the relay near the new fuse box.

run a wire from the positive battery teminal to the relay contact (the one normaly open when relay off and should be shown as such on the relay) and then a second wire from the center contact (the switching bit normaly shown on the relay) to the new fuse box.

(repeat that step if you want to use more than one relay for groups of equipment)

to get the relay to energise you need complete a circuit for the coil. connect one side of the coil to the car body (its mounting point will be good enough and a nice short wire) the other side fo the should be driven from the old fuse box, where you will find a white wire.

If they all look black then clean them up, even the old cars had coloured wire looms and I guess yours all look oil coloured. If you really can't find a white wire then just connect to one side of the fuse box and try it. If it comes on all the time, then the other side will be the switched side and you should be connected there instead. You can then test that by turning the key. The problem is that you don't want the battery connected while you're waving wires about, so put the connection in place connect the battery and try, if wrong then undo the battery change them and try agian.

if you have a meter then you could look for the switched side of the old fuse box but take care probing around when everything is live, find a side of the old fuse box that appears off when the key is off and on when the key is on (the other side will always be on).

anyway

with all that done you new fuse box should now only be live when the car ignition is on.

does that help to make it clearer?

Post by **minor_hickup** » Tue Nov 21, 2006 7:22 pm

Could you not run the power for the new fuse box from the bottom of the existing fuse box on the ignition side. So you would be taking it from the ignition supply and fusing it at the new fuse box?

Post by **Rob_Jennings** » Tue Nov 21, 2006 7:25 pm

you can, but that puts more load on an old switch with things like fog lights etc drawing a lot more current than it was designed for.

It is much better idea to create a new circuit with a relay.

Post by **minor_hickup** » Tue Nov 21, 2006 7:31 pm

Fair point!

Post by **Alec** » Tue Nov 21, 2006 7:46 pm

Hello Sid,

as you say the car is converted to negative earth, all you needed to do to run the stabiliser is to feed it from an ignition fed fuse of the existing loom. Certainly, as you want to extend your system an extra fuse block is sensible especially as it involves relatively heavy loads where additional lamps are involved.

Alec