Electrical Circuit Review

ceedy · Jun 13, 2013

I am trying to add an auxiliary fuse box and initially 3 circuits. I'd like to do it the right way and I was hoping that one of the auto electronic gurus here would bless the circuits that I have designed.

The circuits are for courtesy lights, a rear work-light and an extra set of driving lights. I don't think any of these need to be switched with the ignition (they can always have power).

My questions are:
1) Did I miss anything and will these circuits actually work?
2) Do I need a circuit breaker before my aux fuse box and if so how many amps should it be?
3) Do the colors of the wires make sense for their purpose?
4) Am I better off taking the grounds back to the battery or should I just find a convenient spot on the chassis?
5) Is the "master switch" in the right place for the driving lights?
6) Should the driving lights be switched with the ignition or will the relay serve that purpose (in other words, can this circuit always have power)?

Thanks!

Kwakerman · Jun 13, 2013

Use two relays and two earth cables for the driving lamps (one for each) and two separate earth points on chassis, saves losing both lamps if the single earth or relay fails on your current design (try to reduces the single point of failures).

I also think that if the driving lights are planned to be used as a addition to full beam that they should be wired such that they can only come on with full beam (i.e they turn off automatically when you go to dip) - one for the MOT testers to answer?

Are your courtesy lights LED, if so you could probably come down a wire size or two as 11A cable is a bit ott, would have thought 5A would be more than sufficient in that scenario.

ceedy · Jun 14, 2013

Kwakerman said:
Use two relays and two earth cables for the driving lamps (one for each) and two separate earth points on chassis, saves losing both lamps if the single earth or relay fails on your current design (try to reduces the single point of failures).

That makes sense and should be an easy change.

Kwakerman said:
I also think that if the driving lights are planned to be used as a addition to full beam that they should be wired such that they can only come on with full beam (i.e they turn off automatically when you go to dip)

That is how I want it to work and how I thought it was designed but maybe I am missing something.

I intended for the relay connected to the high beam switch to perform this function. I also want a switch (what I am calling the "master switch") to disable the extra driving lights entirely (If I only want the high beams on and not the extra driving lights).

Thanks I really appreciate the help.

sp00k · Jun 14, 2013

ceedy said:
I also want a switch (what I am calling the "master switch") to disable the extra driving lights entirely (If I only want the high beams on and not the extra driving lights).

I think that's the way to go. That way you can just ensure the switch is off for an MOT and won't fall foul of any rules. I did something similar with my rear worklights which are switched when I select reverse but can also be disabled with an override switch as they could technically result in an MOT failure as they turn night into day.

I ran the + for my aux fusebox from the + on the starter. I fused it through a 100 amp fuse before the new aux fusebox. Fusebox is on the bulkhead behind the seats. You can earth to any point on the chassis or body.

sp00k · Jun 14, 2013

I would put the master switch on the same side of the relay as the high beam switch, that way your switch will not be subject to large loads and you can wire it with light duty wire.

ceedy · Jun 14, 2013

sp00k said:
I ran the + for my aux fusebox from the + on the starter. I fused it through a 100 amp fuse before the new aux fusebox. Fusebox is on the bulkhead behind the seats. You can earth to any point on the chassis or body.

Why did you choose the starter as opposed to the battery?

ceedy · Jun 14, 2013

sp00k said:
I would put the master switch on the same side of the relay as the high beam switch, that way your switch will not be subject to large loads and you can wire it with light duty wire.

That makes a lot of sense.

Here is my updated design:

timtheenchanteruk · Jun 14, 2013

Personally (and what I have done) is have a 3rd switch in there.
the master switch in yours controls the lights, but there's also a SPDT switch between the high beam and master switch, so the feed to activate the relay can be switched from a perm +ve to high beam.
This means if I need to, I can use the front lamps without having the engine running

Kwakerman · Jun 14, 2013

ceedy said:
That makes sense and should be an easy change.

That is how I want it to work and how I thought it was designed but maybe I am missing something.

I intended for the relay connected to the high beam switch to perform this function. I also want a switch (what I am calling the "master switch") to disable the extra driving lights entirely (If I only want the high beams on and not the extra driving lights).

Thanks I really appreciate the help.

You were correct, I missed the bit that said 'high beam switch' and thought you just wanted to manually operate them independent of main beam

ceedy · Jun 15, 2013

Thanks for all of the advise. I am off to order my parts and will report back once I have it all installed.

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