The correct brake light switch for an early c15 seems to be Lucas part 31827, a switch mounted under the left swinging arm pivot bolt which has a lever which acts directly on the brake pedal. I have not been able to find one anywhere in the UK. I have heard that later machines used a pull type switch like the Bantam, mounted on the swing arm under the torque arm bolt with a spring and clamp onto the brake rod. Is this right as this might be the only option unless there is a better solution?
I've used your latter option and used the chaincase through bolt to hold a flat bracket onto which the switch fits, then down to the little clamp
I'm sure someone was selling these at Kempton on the weekend. Its worth keeping up you search. Try e-bay.
I found a couple of places in the States that might help, but cost may be excessive in view of shipping, duty etc.. AFAIK, BSA used the same switch (19-1123) on the C15 until production ended. HTH
https://www.bsaunitsingles.com/item.wws?cpubcode=BSA&sku=31827
https://hdrogers.com/products/nos-lucas-31827-bsa-cycle-brake-stop-light-switch?srsltid=AU7gw4WcSaIAqF9L7ofqb-_DQR0pzoYAK6g3iiCegqfC6irukPRyrm1r
Quote from: Ian C on 21 Sep, 2026, 18:00 I found a couple of places in the States that might help, but cost may be excessive in view of shipping, duty etc.. AFAIK, BSA used the same switch (19-1123) on the C15 until production ended. HTH
https://www.bsaunitsingles.com/item.wws?cpubcode=BSA&sku=31827
https://hdrogers.com/products/nos-lucas-31827-bsa-cycle-brake-stop-light-switch?srsltid=AU7gw4WcSaIAqF9L7ofqb-_DQR0pzoYAK6g3iiCegqfC6irukPRyrm1r
I found a couple of US sites that keep them although, as you suggest it would work out pretty expensive I think. I did find a firm in the Netherlands, Tribsa bits that have the switch but so far I have not translated the website well enough to work out the delivery costs to UK...if they will will deliver that is. The switch was 35 euros which is reasonable. I have not seen a 31827 on Ebay, though there was a switch wrongly labelled as one. Its nice to know that this switch was used throughout production, its an incentive to try and find the right one ;D
Just an update, I have managed to order a new/old stock 31827 brake light switch from Tribsa Parts in the Netherlands. the switch was 35 euro's and carriage 18 euros so £45 in total. not exactly cheap but quite reasonable compared with importing one from the US.
When I needed a sprocket for a Matchless the most cost effective supplier was in Austria!
;D