LED Flasher Unit into Old Lucas 5FL Flasher Can

[svenedin]

I have fitted LED stop/tail lights. I then wanted to fit LED indicator bulbs but as most of you will know, an electronic flasher unit is needed to flash LED bulbs; an old thermal electromechanical flasher unit will not work.

I don't like modifications that change the appearance of the car and the LED flasher units are nasty looking plastic things that look totally different to the old aluminium can type. I believe there is a 3 pin aluminium can LED flasher unit available but only for negative earth. For us positive earthers there is no such thing. Of course LED indicator bulbs DO look a bit different in use (they are brighter) but there is nothing different to see at a car show.

I discovered that the top plate of the LED flasher unit is identical to the top plate of a Lucas SFB100. As I had a broken SFB100 I decided to swap the internals and it worked very well. I am told that this is called "restuffing" in the vintage electronics world. Taking modern internals and putting them into old cans. It is used for capacitors when the appearance of vintage equipment must not be changed.

Anyway, here's how I did it:

You will need an electronic LED flasher unit of the correct polarity for your car. These units must be earthed and have a fly lead for the earth.

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You will also need an aluminium can type flasher e.g Lucas SFB100

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Carefully lever round the edge of the LED flasher unit with a small screwdriver until the top plate pops out

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Then you then can withdraw the internals but note you will have to destroy the outer case to get the fly lead out with its connector still attached. Or, cut off the earth lead terminal and then the wire can be removed through the outer case. You will need to fit a new connector later.

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Now work around the top of the aluminium flasher can, release the top plate and remove the plate and internals

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[svenedin]

Ever wondered what the insides of a thermal flasher unit look like? Now you know.

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Now the LED internals are placed in the aluminium can but there's the earth lead. You could drill a little hole in the bottom of the can and feed the lead through there or do what I did and file a space in the top plate with a rat's tail file

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Now put the LED flasher stuff into the aluminium can and push the edges over with a small screwdriver so that it is secure.

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[svenedin]

Finally fit in the car and screw the earth connector down under a convenient screw.

You can now flash LED bulbs or any combination of LED and incandescent bulbs. Handy if a bulb blows and you only have an incandescent bulb to hand.

Note: if you have hazard lights this uses a dedicated flasher unit which must be LED compatible to flash LED bulbs.


Stephen

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[svenedin]

Just for completeness, if you have a hazard system that has a 2-pin Lucas thermal flasher unit 9FL, there is an identical format LED compatible flasher unit from Lucas WW10059E

https://www.feked.com/genuine-lucas-led ... UWrvZJTt2j

Since doing this, I have thought that a more elegant solution would be to rivet the earth fly lead to the inside of the can. Then the metal can being attached to the bulkhead becomes the earth and no fly lead visible. Soldering onto aluminium is difficult hence the idea to rivet instead. If done at the back of the can it would not be visible.

Stephen

[Andmurph]

Nice work Steven. How does the clicker sound? I’d guess the can amplifies it slightly which would be no bad thing.

[svenedin]

Nice work Steven. How does the clicker sound? I’d guess the can amplifies it slightly which would be no bad thing.

Thanks Andy. It was a bit of fun.

The clicker is good and I can hear it at low speeds but I won't be able to hear it at higher speeds due to engine noise drowning it out. Another option to keep things looking original is to leave the thermal flasher on the bulkhead but instead of it being connected as normal, make an extension for the 3 wires that connect to the flasher unit. Male to female connectors, feed the 3 extension wires (in the correct BS-AU7 colours, bundled into one with heat shrink insulation) through the bulkhead and mount the new LED flasher unit under the driver's side glovebox. Then the bulkhead looks original and this has the advantage that the clicker should be much more audible. I don't need to do this though as I have a clicker (all it does is make a click, it isn't a flasher unit) but I haven't got round to installing it yet. It needs the driver's glovebox out to access the indicator wiring and I really don't like that job (horn push out, steering wheel off, indicator assembly off, rotate outer steering column etc etc).

Stephen

[svenedin]

As I am an inveterate fiddler, I moved the LED flasher to under the driver's side dashboard. It is easier to hear it clicking there. The old thermal Lucas FL5 is still on the bulkhead but is not connected. It could be re-connected, if needed again, in about 30 seconds. I made a little sub-loom of the 3 wires that go to the bulkhead flasher can: light green (pilot), green (live), green/brown (flashed output) and connected that to the bulkhead female spade flasher wires with male spade connectors. The I fed the new wires through the bulkhead. The LED flasher unit is just strapped in with a cable tie for now and the earth wire is going to a very convenient female earth bullet sleeve that was right there. There is a metal mounting clip available for this LED flasher and when I get one I will mount it to that as there is already a hole in the right place in the metal floor of the glovebox area. The earth can then go to the mounting clip bolt.

Stephen

Original type thermal Lucas FL5 on bulkhead. Not connected and its wires now connecting to an extension going back through the bulkhead to the LED flasher unit

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Under the driver's side dashboard. In front the hazard wiring (original Lucas SFB300, not a modern copy) with in-line fuse and silver FL9 flasher unit mounted with an adhesive pad. Behind the round plastic LED flasher unit temporarily mounted with a cable tie and earth wire going to a very handy female bullet sleeve that is exactly in the right place. Intention to get the metal mounting clip for the LED flasher unit and mount the earth wire to the clip fixing bolt. Hazard system needs an LED compatible flasher unit. Lucas make one in identical format to the FL9.

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