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Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 12:05 pm
by svenedin
Somebody asked me about this so I thought I would dig out some of my photos.
This isn't a "how to" but just a suggestion of how a Lucas 155SA/SFB300 hazard light unit could be installed in a convertible Minor (especially a late convertible).
The problem is two-fold. Firstly, the under-dash space is very limited in a convertible due to the strengthening arches. Secondly, the raised lip under the dash limits the depth available and the Lucas unit is too deep to fit.
The hazard switch can be removed from the original bracket and fitted into a suitable switch panel (15mm hole) or the dashboard could be drilled (although I think doing such a thing is vandalism!).
Another way is to use the original bracket but shorten it considerably so that the switch can be mounted under the dash in front of the raised lip. Then the FL9 type relay can be mounted behind the raised lip to the side. Sticky pads can be used to attach the brackets to avoid the need to drill anything.
Second hand 155SA turn up at £10 or less. The modern copy is around £30 at the time of writing. It is a good system. The indicator switch circuit to the FL5 flasher unit is disabled when the hazard lights are switched on and the switch flashes to warn that the system is active. Unlike some modern kits, all the wiring is the correct BS-AU7 colour code standard.
Stephen
Lucas 155SA unit (original). This is sold as a modern copy as SFB300

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 12:08 pm
by svenedin
The restricted space in a late convertible Minor, made worse by the heater control taking up space as well.

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Bracket is too long

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 12:12 pm
by svenedin
Marking the bracket to be shortened. It is back to front to work out how much to shorten it.

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Scribed and ready to cut with a hacksaw

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The shortened bracket. Sharp edges removed with a file.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 12:16 pm
by svenedin
Showing roughly how the switch and relay would be mounted when on the car

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Test fit. NOTE: the terminals on the back of the switch must not touch any metal of the car. The switch must be mounted sufficiently far forward to avoid this.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 12:22 pm
by svenedin
Tip: it is better to drill holes for screws to attach the switch bracket rather than use adhesive pads (I say this as somebody who hates drilling holes in my car). This is because the switch bracket can make it even more awkward to remove or fit the glovebox surround. If the bracket is stuck on it cannot be easily removed for maintenance. The relay, which is held in the other part of the bracket can be stuck on with sticky pads.
Stephen
This is the other part of the bracket that was cut in two. You can mount the relay out of sight under the dashboard and it is easily changed if required.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 4:14 pm
by svenedin
Finally, the instructions.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 4:33 pm
by Bill_qaz
Surprised by the restriction due to the strengthening plate of the convertible. As well as the corner gusset is the bottom lip also deeper between the two sides? Don't remember the bottom lip being in the way on my saloon, where I have hazard unit, which looks like it would be past the point where your corner strengthening ends.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 4:38 pm
by svenedin
Sorry the photo is out of focus. The lip is continuous along the entire length under the dashboard and joins the strengthening arches in either corner.
Your car is earlier and has the driver's side glovebox with lid. The later ones have a surround which can be removed.
Stephen

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 4:54 pm
by Bill_qaz
Sorry blurred pics looking at the heater control mount yours compared to mine it appears the convertible has a deeper flange.
Its only out of idle interest but I'll try and get a clear pic next time I visit the car and maybe even measure

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 5:01 pm
by svenedin
It's easier to show the passenger side because there's nothing in the way.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 5:10 pm
by Bill_qaz
It could be just an illusion or maybe my hazard switch body is lower from the mounting face than your Lucas as it fits past the lip. I can't remember the make. I can't look at the car as it's in storage. Not important just curiosity

Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 5:13 pm
by svenedin
I suppose it keeps it interesting that what fits in some cars doesn't in others!
Storage? If your Morris OK?
Stephen
Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 6:06 pm
by Bill_qaz
Yes no issues, it's always kept in storage when not being used. Inconvenient as 1/2 hour away, but safe as no off road parking at home, they didn't build too many garages or drives 400 years ago
But its very convenient for working on it though, with 4 post lift etc and warm in winter.
I don't tend to use it from November until spring but gives me time to work on it and do whatever is needed.
Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Fri Nov 07, 2025 6:14 pm
by svenedin
Bill_qaz wrote: ↑Fri Nov 07, 2025 6:06 pm
Yes no issues, it's always kept in storage when not being used. Inconvenient as 1/2 hour away, but safe as no off road parking at home, they didn't build too many garages or drives 400 years ago
But its very convenient for working on it though, with 4 post lift etc and warm in winter.
I don't tend to use it from November until spring but gives me time to work on it and do whatever is needed.
Fair enough. When I was a student I had a similar situation and the Morris lived in a garage 30 minutes away by bus. It was completely impractical to keep a convertible parked on the road in central Edinburgh. I lived in Tolcross but the Morris resided in the far more upmarket Morningside!
Stephen
Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Sat Nov 08, 2025 6:19 pm
by geoberni
svenedin wrote: ↑Fri Nov 07, 2025 5:01 pm
It's easier to show the passenger side because there's nothing in the way.
Stephen, your late car, or perhaps because it's a soft top, has a different seam.
Images of my Hazard Switch (genuine 1975 item which I had) as fitted to my SII.
Note the edge joint of the 2 sheets of metal, whereas yours appears to have the rear metal, being the base of the shelf like piece under the glovebox liner, folded up over the front.
The lip is about 12mm, 1/2".

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Sat Nov 08, 2025 7:07 pm
by svenedin
Berni,
Nice period very in keeping switch! The Lucas 155 SA in my pictures is also original. I found it wrapped up in newspaper from the 1970's.
Yes the soft-top is definitely different under the dashboard. To ascertain exactly how it differs from a standard car I would have to have the two next to each other and do some measuring. Something to do next year during the car show season!
Stephen
Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Sat Nov 08, 2025 7:44 pm
by Bill_qaz
geoberni wrote: ↑Sat Nov 08, 2025 6:19 pm
svenedin wrote: ↑Fri Nov 07, 2025 5:01 pm
It's easier to show the passenger side because there's nothing in the way.
Stephen, your late car, or perhaps because it's a soft top, has a different seam.
Images of my Hazard Switch (genuine 1975 item which I had) as fitted to my SII.
Note the edge joint of the 2 sheets of metal, whereas yours appears to have the rear metal, being the base of the shelf like piece under the glovebox liner, folded up over the front.
The lip is about 12mm, 1/2".
20251108_105433.jpg20251108_175103.jpg
Berni whats the bit that has pull stamped on it?
Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Sat Nov 08, 2025 9:32 pm
by geoberni
Bill_qaz wrote: ↑Sat Nov 08, 2025 7:44 pm
geoberni wrote: ↑Sat Nov 08, 2025 6:19 pm
svenedin wrote: ↑Fri Nov 07, 2025 5:01 pm
It's easier to show the passenger side because there's nothing in the way.
Stephen, your late car, or perhaps because it's a soft top, has a different seam.
Images of my Hazard Switch (genuine 1975 item which I had) as fitted to my SII.
Note the edge joint of the 2 sheets of metal, whereas yours appears to have the rear metal, being the base of the shelf like piece under the glovebox liner, folded up over the front.
The lip is about 12mm, 1/2".
20251108_105433.jpg20251108_175103.jpg
Berni whats the bit that has pull stamped on it?
That's my genuine 1950 Fire Extinguisher. Still with a full charge of Carbon-tetrachloride, as used in the more common Pyrene ones.
brought from Fleabay, expected it to be empty, but it had an un-operated canister inside.
Nu-Swift made the basic can with a strike knob on top, where you hit it and pointed it at the fire until it ran out, or the same can could go in the 1000 model which had a controlled release lever on top.
Mine is a 1950 head, a 1951 Case, and the refill inside is dated 1963, but that's hidden when assembled.
Push up on Black bit to release from mounting frame, Pull on Chrome bit to operate. Just don't breath in the CTC in a confined space.

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Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Sat Nov 08, 2025 9:35 pm
by svenedin
geoberni wrote: ↑Sat Nov 08, 2025 9:32 pm
Bill_qaz wrote: ↑Sat Nov 08, 2025 7:44 pm
geoberni wrote: ↑Sat Nov 08, 2025 6:19 pm
Stephen, your late car, or perhaps because it's a soft top, has a different seam.
Images of my Hazard Switch (genuine 1975 item which I had) as fitted to my SII.
Note the edge joint of the 2 sheets of metal, whereas yours appears to have the rear metal, being the base of the shelf like piece under the glovebox liner, folded up over the front.
The lip is about 12mm, 1/2".
20251108_105433.jpg20251108_175103.jpg
Berni whats the bit that has pull stamped on it?
That's my genuine 1950 Fire Extinguisher. Still with a full charge of Carbon-tetrachloride, as used in the more common Pyrene ones.
brought from Fleabay, expected it to be empty, but it had an un-operated canister inside.
Nu-Swift made the basic can with a strike knob on top, where you hit it and pointed it at the fire until it ran out, or the same can could go in the 1000 model which had a controlled release lever on top.
Mine is a 1950 head, a 1951 Case, and the refill inside is dated 1963, but that's hidden when assembled.
Push up on Black bit to release from mounting frame, Pull on Chrome bit to operate. Just don't breath in the CTC in a confined space.
20210314_115711.jpg20210314_115631.jpg20210314_163301.jpg
The carpets get dry cleaned at the same time as putting the fire out!
Stephen
Re: Lucas 155SA/SFB300 Hazards in a convertible Minor
Posted: Sat Nov 08, 2025 11:04 pm
by geoberni
svenedin wrote: ↑Sat Nov 08, 2025 9:35 pm
The carpets get dry cleaned at the same time as putting the fire out!
Stephen

brilliant.
