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Replacing rear brake light switch


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Unfortunately my switch has stuck or gone us, so as I have to take it out to find what is wrong I might as well fit a new one.

As the switch is in an awkward place is there any easy way of getting it out.

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Leave the old one where it is and fit a new one on the pedal box.  The wires will reach so no changes needed.

https://www.gsparkplug.com/brake-light-switch-lucas-smb429-replaces-1368786-61311350645-61311368786.html?___SID=U

It fits in the hole where the bolt is that limits the travel.  It has the advantage that the light comes on as soon as you hit the pedal rather than when hydraulic pressure builds up. Gives people behind a tad more notice. 

 

brakesw.jpg.260523610ecfc487fc3bbc35b026bb69.jpg

Edited by RobH
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If the car is still fully Lockheed braked.....

Bit more work on a Lockheed car as the pedal box has welded nuts to screw pedal stops into.  That thread is wrong for the mechanical switch.

Make up a bit of bent steel bracket-work to hold the switch and clamp as and where you can with the plunger pointed as the pedal - Just like a TR4/4A

The wiring will need extending as the Lockheed pressuer switch on a RHD car is on the RH side of the engine compartment.

Still a good modification away from the pressure switch.

 

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As noted it is a bit more work to do this on a TR2/3 with Lockheed brakes. As an alternative I rigged up a switch under the dashboard directly onto the brake pedal. A small piece of timber araldited into position and a bit of glue and a length of wire.

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Would it be OK to use parts of this session in an article for TRA about the hydraulic brake light switches? The solution from RobH has the most originality sympathy I have seen. Just one question though, how is the piston shaft rod's slack adjusted? Does the swtich take the full load of a released peddal?

My orginal Lucas switch (I do believe it was the original one fited in 1955) finaly failed 3 years ago. The replacement failed after 9 months and it's replacement from a deliberately different OEM failed this year. I have sectioned them on a mill and the result is that thesee modern replacements were very poorly made and of difrerent internal design. I have now fitted a salvage part from my spares shed but if this fails it looks like a electric switch is, sadly, the only way as the new parts I have experienced are not fit for purpose. Also, the confusion over threads continues and made worse by the fact that some of the variations seem to be no longer available.

MJ

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Mike the later sidescreen cars didn't have the travel-stop bolts fitted to the pedal box anyway, so the switch doesn't take any load as such. Adjustment is by positioning the switch body so the switch plunger is just operated when the pedal is at rest. There is more switch travel available so the pedal is not forcing anything.

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On 9/13/2021 at 9:29 AM, mikej said:

Would it be OK to use parts of this session in an article for TRA about the hydraulic brake light switches? The solution from RobH has the most originality sympathy I have seen. Just one question though, how is the piston shaft rod's slack adjusted? Does the swtich take the full load of a released peddal?

My orginal Lucas switch (I do believe it was the original one fited in 1955) finaly failed 3 years ago. The replacement failed after 9 months and it's replacement from a deliberately different OEM failed this year. I have sectioned them on a mill and the result is that thesee modern replacements were very poorly made and of difrerent internal design. I have now fitted a salvage part from my spares shed but if this fails it looks like a electric switch is, sadly, the only way as the new parts I have experienced are not fit for purpose. Also, the confusion over threads continues and made worse by the fact that some of the variations seem to be no longer available.

MJ

Hi Mike,

Original N.O.S. switches can be found with a bit of diligent searching.

Over the years Lucas manufactured different versions, so it important to buy and install the correct version.

Have you reviewed the very detailed article written by Ian Gibson entitled "Hydraulic Brake Light Switches". 

If you require reference photos of various switches I think I may have a few N.O.S. spares.

Regards, Richard

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