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Thread: rewiring project

  1. #1
    Join Date
    Dec 2014
    Los Angeles

    Default rewiring project

    One of the issues I ran into when constructing my Birkin was the electrical system. I realize that it was designed in South Africa to comply with the requirements of a variety of countries while meeting cost considerations. In particular, I didn’t like the plastic rocker switches. Neither was I happy with some of the gauge locations. After living with the car for over a year after completion, I decided to do something about it.

    I ended up cutting a new instrument panel from 14g aluminum sheet using knockout punches (3 1/8” and 2 1/16”) as well as step drill bits. This allowed me to use toggle switches to replace the rockers. One of the problems that arose was finding toggles that would function the same way due to how the car was wired. I have now investigated nearly every toggle switch on the internet and none, to my knowledge, fit the bill for replacing the rocker style hazard switch. The real issues centered around how the indicator and hazard lights are wired. I ended up reconfiguring the wiring to use a 5 pin relay to switch the power supply between the indicators flasher and the hazard flasher. Since I have committed to running Brooklands windscreens, I could utilize the existing windshield demister relay. I am attaching a schematic as well as the following description of the process. These instructions are unique to the Birkin but describe a strategy that could be applicable to any kit car.

    Both the indicator lights and the hazard lights each use a 10a fuse. This modification eliminates both and uses the windshield demister slot to hold the 10a fuse for the new circuits instead. Proceed as follows:

    1. Remove the battery and scuttle.

    1. Label the cluster of connectors for each existing switch clearly (take pictures as well).

    1. Remove the relays and the relay cluster. Note that there is very little slack in the wiring harness. The relay bases separate by sliding apart front to rear.

    4. You will need an extraction tool to release the connectors from slot 87 and 87A from the demister relay base. Slide an inch
    or so of heatshrink over the connectors and reduce it to protect them.

    5. Perform the same task on the 49 slot of the bases for the indicator and hazard flashers.

    6. Connect the wires from the old demister switch to the two poles of the new toggle switch. This switch now controls the
    old demister relay (pin 85).

    7. You now need to fabricate two lengths of 16 or 18g wire of a sufficient length to run from this relay to the outboard flasher
    bases. You will need ” “Ford" female spade connectors (I found mine at Pep Boys). These connectors have a small retaining tab
    on the back to hold them in place in the base.

    8. Connect slot 87A to indicator flasher slot 49. Connect slot 87 to hazard flasher slot 49.

    9. Verify that the existing G/w wire from indicator slot 49A runs to the center pin on the directional switch.

    10.The hazard output (49A) connects to all four indicator lights and treats them as one. We need to maintain the separation of each
    side in order for the directional to work so we need to install a diode in both the left and right circuits. Think of it as a
    one-way check valve for current. You will need two 6a50v diodes (Maybe you could use smaller. I’m no electrical engineer.). I
    picked up a small “project box”, about 1 ” x 2” to house and protect the connections. The ends of the diodes with the stripes

    are mounted toward the light bulbs. The other ends are soldered to the grey wire (12v regulated feed) from hazard flasher pin
    49A. This connection is located near the original harness location about mid dash. The other ends are soldered to the green and
    yellow wires as appropriate to segregate the signal. Drill holes in the ends of the box as needed. I lined the box with a thin
    layer of foam and secured it to the existing harness bundle with a ziptie.


    Continually verify continuity as you trace wires. I carefully soldered all connectors and covered them with heatshrink tubing.
    If you change over to LED tail light bulbs, use CANBUS bulbs. They will correct for the reduced load of the LEDS to reduce
    hyper-flashing. If the turn signals flash together, you may still need load-reducing resistors in the circuits.

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