LED Flasher Unit into Old Lucas 5FL Flasher Can
Posted: Sat Oct 03, 2026 7:37 pm
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.
You will also need an aluminium can type flasher e.g Lucas SFB100
Carefully lever round the edge of the LED flasher unit with a small screwdriver until the top plate pops out
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, No going back now......
Now work around the top of the aluminium flasher can, release the top plate and remove the plate and internals
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.
You will also need an aluminium can type flasher e.g Lucas SFB100
Carefully lever round the edge of the LED flasher unit with a small screwdriver until the top plate pops out
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, No going back now......
Now work around the top of the aluminium flasher can, release the top plate and remove the plate and internals