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Brake light hydraulique/electrique switch


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hello Everyone.

 

New Forum member from France. I bought a TR3A about nine months ago;

 

34861014386_a49459a3ae_b.jpgP1040454 by john curtis, sur Flickr

 

Have had a love of cars since teenage times and have had the luck to own and race Aston Martins and rallying with Escort Twin Cam and Austin Healey etc.

 

I have just changed the brake switch on the TR3A and replaced it with one from Moss.

I had complete brake failure, luckily reversing out of the workshop and not on a rallye. The fluid had drained through the thread on the switch. I now see that the replacement switches do not have a tapered thread like the originals. Spoke to Moss who apologise and say they will send me a copper washer which should sort it.

Has anyone else had this problem ? Nothing is mentioned in their catalogue and no washer is shown.

 

Unfortunately the fluid has ruined the paint on the chassis. Moss are sending some chassis paint but I doubt if it will match. At least it was a gesture.

 

Why can't we have original equipment? I would be happy to pay more. i suppose it is cheaper to cut a parrellel thread.

 

 

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There has always been two types of threaded switch one with parallel thread and one with a tapered thread unfortunately the only way to find out is to take it out to check and then order accordingly.

Stuart.

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Thanks for the replies. I have the Girling system.

I am not too good on recognising threads but the replacement switch (21B291 Girling) is a looser fit and the diameter of the thread is about 1mm less than the existing one. Also the existing switch tightens before reaching the cruciform union. This makes me think it is a tapered thread.

How am I doing ? !!

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Hi John,

I should have welcomed you to the forum - Welcome.

 

If you have a Girling system then the thread should be parallel.

Could your existing fitting on the chassis be a tapered Locheed fitted by a PO. That may explain the looseness of the switch.

 

If you do have a tapered female fitting I wouldn't use a parallel male, even with a copper washer, as it will be attached by only a few threads.

 

Nice looking car by the way.

 

Roger

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The cruciform union would seem to be Girling.. It has the restrictor valve and the fitting to the bracket on the chassis.

Is it as Stuart said that I could have the Girling system with a tapered thread.

Does my description indicate that the thread is tapered ?

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You never know whats been done in the intervening 60 yrs but if the previous switch was a tapered thread and fitted correctly to the union then its safe to assume thats what you need to replace it with and to I have come across both types fitted to 3a`s so never assume Roger!

Dont fit the wrong switch get the correct one.If you order that switch from TR Shop they usually ask what thread it is as a matter of course.

Stuart.

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Does my description indicate that the thread is tapered ?

 

I am not too good on recognising threads but the replacement switch (21B291 Girling) is a looser fit and the diameter of the thread is about 1mm less than the existing one. Also the existing switch tightens before reaching the cruciform union. This makes me think it is a tapered thread.

Edited by TwinCamJohn
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For we non purists.....

 

Fit the failed taper threaded switch that you know seals back in the union and then fit a mechancial BMW/Mercedes brake switch up at the pedals/master cyls. The wiring extends very easily and the metal cased switch looks period, rather than the replacement ghastly plastic thing for TR4-6. This mod has been detailed on this forum before.

 

This style, but check operation - depress plunger is off.

http://www.ebay.co.uk/itm/2-Pin-White-Housing-Intermotor-Brake-Light-Switch-Rear-Safety-Genuine-OE-Quality-/191419280982?fits=Car+Make%3ABMW

 

This has been my experience of the modern batch of hydraulic switches - the replacement hydraulic switch survived no more than a year. The first indication of failure is it only working when the pedal is pressed VERY hard.

 

Cheers

Peter W

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  • 6 months later...

My Hydraulic activated switch failed a couple of days ago - the brake lights stayed on whether my foot was on the pedal or not. a few taps on the switch with a small hammer did not make any difference, so decided to go down the mechanical switch route. Most difficult part was removing the captive nut originally intended to take the limit stop screws (see clutch side) these were deleted anyway on later cars. Managed to remove it using a long 13mm ring spanner on it, & twisting till it came away. The hole then had to be enlarged to just under ½" to take the "BMW" switch (£5.90 from Car Parts 4 Less" on ebay). The rest was easy:

 

 

post-12009-0-75273700-1514046453_thumb.jpg

 

Bob.

 

P.S.

Have looked at the photo, I might just re-crimp that left hand spade :o !

Edited by Lebro
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Theres an alternative solution in one of the Devon Group In The Garage newsletters for those who may want to retain the pedal stop and have a lot more spare time to make the change ????

 

http://www.tr-register.co.uk/group/devon/social-report/2017/10/0855/In-the-Garage-Autumn-Edition

Edited by Drewmotty
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