BRAKE LIGHT SWITCH (a saga)
by Lorne Goldman at the eMog Pub 2011

1. Recent Developments
2. Replacements
3. Wiring in a relay

RECENT DEVELOPMENTS

If you are reading this, it is likely your Morgan brake light switch failed..maybe a few times already. Not to worry, you are now member of a large club! Just in case, you can test by removing the wires from the brake light switch and "jumping" it with a wire in between. If your brake lights go on, the switch is defective.

For some reason. the hydraulic brake light switches seem to fail regularly in the last few years (# SPB 401..seems to be a Lucas) so much so that the Factory has moved to a mechanical switch. Image on the right.

Sadly, the Factory mechanical switch option is very costly and invasive. As it is mounted in front of the pedal, it cuts into the precious footwell space..especially for those of us with longer legs.

REPACEMENT OF THE EXISTING SWITCH (A BIG WATCHPOINT!!!)

These switches are fitted in the car to a 4-way junction inside of the brake side valence (inner wing)..either forward next to the pertinent front wheel (post 1993 cars) or close to the Master Cylinder. The way the factory fit the 4 way junction is key to the installation.

The 4 way junction has a single fitting screw. In the Morgan parts book, the junction is shown with the fitting held to the frame flange below. This is correct. It prevents the junction rotating as you unthread or thread the brake light switch, preventing the metal brake lines from being turned with the junction. (OUCH!)  Sadly, many of these junctions were installed by the Factory with the fitting screw through the valence rather than the frame flange. See where your junction fitting screw is before you remove the switch. Look at the pictures.

If it is fitted through the valence, BE CAREFUL. You have three options. You can remove the brake lines and switch, drill and refasten the junction through the frame flange, refit the lines and switch to the newly oriented holes (they all have the same thread) and bleed the brakes. Alternatively, you can hold the junction with big vice-grips or a pipe wrench to stop it from turning with the switch.

I have learned to use a socket and a very quick "slap" to loosen the switch enough so it does not turn the junction. A slow steady force WILL turn the junction when the switch is tight. See the diagrams.
 

REPLACEMENTS POST -1975 switches

Though a perfect and inexpensive mechanical switch would be an ideal solution, until one is sourced, we need an immediate easy solution. (Often these turn out to be permanent anyway!). The first thing is to avoid the Factory original, the SPB 401. Along with being dear, (£14 in the UK) and triple that from aftermarket suppliers in North America., they often last only a short time. The original switch is a 3/8" UNF.

There is a popular replacement in the UK, an Intermotor part which sometimes lasts a bit longer.  The Intermotor part number for the post 1975 cars is 51610. (I have been told the Facet is 71099 and Webcon is WBL087 but unconfirmed as yet.  The same switches were used on the Lotus Elan  61-75,  Jaguar e-types, Europa  69-76,  Seven Twin Cam  1972,  Super Seven  63-72, Reliant  Rebel  69-74,  Rover  2000 & 2200  63-77, and the  3500 from 68-72. The Singer Chamois  64-71.  Gazelle 61-71.  Humber Hawk 62-68. Super Snipe 64-66. Imperial 64-68.  Sceptre 63-76.  Hillman Hunter 66-79.  Husky 62-72.  Imp 63-76.  Minx  61-71.  Talbot  Sunbeam  69-76.  Singer Vogue 61-71. This will help the owners in the UK, but not elsewhere and it must be accepted the risks of occasionally driving without breake lights.

In North America, I have found a replacement for the post 75 switch that has now lasted longer than anything I have tried before. It is Welles RB 401. It would seem that it is not exactly the same thread as the UK sourced product but I beleive the imperceptible difference is a function of more precise manufacture. I took the precaution of buying a spare brake junction and the Welles product threads in with little effort. The original Intermotor and the Welles can all fit in the same socket without an issue or leaking. Frankly, the Welles switch is available everywhere. I got mine discounted from World Discount, (716 877 2458) in Buffalo NY. The contact is NEIL and he will now sell and post anyone who calls. At $3.45 (£1.90) each, buy more than one and carry an extra with you! (You should do that with any brake light switch you buy.) It is now the end of the 2014 Morgan season. I have now put another 35000 miles on the Welles switches between two Morgans. The switches have neither leaked nor failed. Those I gave my spares to report the same success. For those who are not convinced, I recommend they source and always carry two of the UK switches listed above and wire in a relay.
 

PRE-1975 SWITCHES THAT ARE COMPATIBLE

Earlier switches last much longer than the MMC supplied ones.

For the pre-1975 cars, the earlier switch (Lucas SPB 400 and 1/8" x 27NPTF) corresponds to a Intermotor 56100.) The original was also used on the Alfa 1750 from 68-72, the 2600 in 62-68, the Giula 62-71. The Fiat 500 from 55-75, 600 in 56-68, the 1100 54-68,  1200  66-70. The Ford Anglia 59-68,  Jaguar e-type 1967, Capri, Classic  61-64. Corsair 1500 GT  63-66. Corsair V4 66-70. Cortina 1, 11  62-70. Escort 1  1/3 GT  68-71.  Zephyr 4,  6  62-72,  Zodiac  62-72. In the Jaguar  2.4, 3.4. 3.8 from 63-69,  E Type 1-72,  Mk 10 62-70,  Sovereign 2.8  4.2  66-70,  XJ6 2.8,  4.2  68-71.  Lotus  Cortina 1,  11  63-70.  MG  1100  1300 63-71. MGA 58-62. MBB GT 63-74.  MGC GT 68-74. Magnette 67-68, Midget 61-74,  Reliant Regal 63-74,  Riley Elf 62-70,  Kestrel 1100 69-70. Austin 1100 1300  62-74, 1800  65-67,  A40  61-68, A60  67-69.  Mini-Cooper  58-69. Morris  Minor  62-71. Oxford  67-71.  Seat 600 D, E, L,  63-73. Triumph  Spitfire  63-67. TR4, A  62-67. Vanden Plas Princess 64-74.  127  71-83,  128  69-89,  1300, 1500,  66-70. Volvo 121, 122, 131, 221 from 61-68. and the 1225, 123, 222 from  61-70. The Wolseley 1100, 1300  66-71, 16/60  69-70 and the Hornet from 61-69.

WIRING IN A RELAY

 

Our Morgan brethren in France, (found on the excellent Le Bar des Morgans) have an idea that is less invasive than many other solutions. Each time you press your brake pedal, the switch is impacted with 3.5 amps current (with 2 stop lights) or 5.2 amps (when you have a 3rd stop light). Reduce that opening current impact and you will extend the life of the switch. This can be done by adding a relay in the circuit. It reduces the impact on the switch to a few milli-amps. The lifetime of contacts is extended accordingly.