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Thread: BN4 Wiring Questions

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    Jedi Hopeful Csarneson's Avatar
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    BN4 Wiring Questions

    After a ton of terrified procrastination I'm finally getting around to installing a new wiring loom in my 57 BN4 basketcase. The car was in tiny pieces when I got it and everything electric is covered in 1/4" of grime and severely decayed. No wiring colors are visible and most of the relays have been reduced to grubby little nuggets. I'm doing my wiring from scratch it seems. The wiring diagram helps but doesn't show me anything about how things are routed.

    There are 4 stubby blue wires coming out of the main harness at the main firewall grommet. Are these for the dipper (foot) switch? Should these wires be in front of the firewall or behind it? None of the pictures I see actually show this hooked up in any fashion that shows me how it is connected and routed. I'm trying hard to understand this harness but these wires have me stumped. Why would they be spliced by bullets at the firewall? If they are the dipper wires then why splice them at all? Wouldn't just another long loom leg have been better? What am I missing?

    Thanks guys.

    Chris
    Last edited by Csarneson; 05-16-2018 at 07:57 PM.

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    Jedi Warrior roscoe's Avatar
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    Re: BN4 Wiring Questions

    I do not know if you have done this sort of routing before but I'm happy to give you insight into how I did my BN2. First, I laid out all the harness segments and proceeded to label ALL of the wire ends based on the colored wiring diagram that was in the shop manual. This was a winter project for rainy nights around the wood stove. I can't tell from your description if the old harness is still in place or not. When you say no wiring colors are visible, I assume you are referring to the old harness. If you cut or pull back the fabric, you will probably see wire colors that look recognizeable, although a good light and magnifier are sometimes necessary and if you are red/green color blind you are screwed. Of immense help were photographs I obtained from British Car Specialists in Stockton CA that were sold to me in an album; I believe they still sell sets for various big Healey models. Lots of routing issues were resolved with those and a CD I found on line and bought for a few bucks that had close up photos of many portions of the wire harness. My point is that such photos are invaluable. If someone can just get you a few under dash shots and as many more of where the harness ends terminate it will reveal all that you need. The factory may not have always done things the best way but as far as routing, you don't have too many viable options unless you really want to go all out and make things logical, safe and simple (and blow off originality). The Lucas bullet connectors are nasty little buggers and I can only hope modern British cars have moved on. I definitely had some AhHa moments when something I had been trying to do turned out to be wrong. I do believe that Mr. Rube Goldberg must have been deeply involved in Lucas' business. Collect photos, do not be discouraged, carry-on.
    Jon Robbins
    1956BN-2 (do it all yourself, you'll be glad you did)

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    Jedi Hopeful Csarneson's Avatar
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    Re: BN4 Wiring Questions

    After more research I am nearly certain that the 4 wires are for the dipper switch harness. I think I am going to choose to move those wires inside the firewall and then I can hide a couple relays behind the dash.

    I'm slowly working my way through the harness. Thanks Roscoe.

  4. #4
    Duane_Rhynard
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    Re: BN4 Wiring Questions

    Quote Originally Posted by Csarneson View Post
    After more research I am nearly certain that the 4 wires are for the dipper switch harness. I think I am going to choose to move those wires inside the firewall and then I can hide a couple relays behind the dash.

    I'm slowly working my way through the harness. Thanks Roscoe.


    Sorry I'm so slow in replying!

    You are correct, these are for the floor switch for the hi-low beams. The four wires from the main harness turn into 3 at the bullet connectors that connect to the pigtail for the floor switch (See your wiring diagram).

    Pictures of my BN6 below, (Same as your BN4 only a different covering on the harness). The wires are routed as shown and enter the foot well through the shown grommet. You will want to add the relays before the floor switch to limit the current draw through the dash headlight switch (Side head).

    I added my relay on the inside wall next to the steering column, and my additional fuse protection near the drivers vent (LHD) as shown in the last two images.

    Let me know if you need anything else!

    Duane












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    Jedi Hopeful Csarneson's Avatar
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    Re: BN4 Wiring Questions

    Wow! Thanks! I was definitely confused on the 4=>3 thing. This helps. So it looks like you left your original fuse block in place and installed a secondary box under the dash. I love that concept and I think I will copy it. Where did you connect your hot wire to a switched/unfused white? Is it one of the 4 whites at the old fuse block?

    Am I correct in assuming you have a single relay then for your lights as opposed to a relay on each leg after the dipper? If I understand correctly you are putting the full current through your dipper switch still. Wouldn't two separate relays be preferred which would lower the current through your dipper as well?

    Also, on the last picture what is the item on the far right with the fat black wires? Is it one large fuse on the main power coming from the solenoid? If so, why?

    Thanks again Duane!
    Last edited by Csarneson; 05-18-2018 at 11:49 PM.

  6. #6
    Duane_Rhynard
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    Re: BN4 Wiring Questions

    Quote Originally Posted by Csarneson View Post
    Wow! Thanks! I was definitely confused on the 4=>3 thing. This helps. So it looks like you left your original fuse block in place and installed a secondary box under the dash. I love that concept and I think I will copy it. Where did you connect your hot wire to a switched/unfused white? Is it one of the 4 whites at the old fuse block?

    I connected +12V power from the voltage regulator from the A1 terminal through a fuse to my secondary fuse block.

    Am I correct in assuming you have a single relay then for your lights as opposed to a relay on each leg after the dipper? If I understand correctly you are putting the full current through your dipper switch still. Wouldn't two separate relays be preferred which would lower the current through your dipper as well?

    Yes, I'm still running the full power of the headlights through the floor switch. I did this since I have never had a failure with any floor switch, just the dash switch. In my opinion the dash switch is undersized to handle both the parking/running lights and headlights. I'm still running the parking/running lights (LEDS) through the dash switch, but the headlights go through the relay.


    Also, on the last picture what is the item on the far right with the fat black wires? Is it one large fuse on the main power coming from the solenoid? If so, why?

    I installed an original Smiths ammeter and the fuse is to protect the the ammeter system from any unauthorized shorting of the ammeter wires to the chassis. (See images below.)

    Thanks again Duane!

    Let me know if you have any more questions!

    Duane





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