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It is MOT time again and the brake light switch has failed, changing this is now an annual event, luckily it is simple and reasonably inexpensive (£6.00 inc P&P). The type on my car is the tapered thread and now spade connectors (it should use screw terminals).

 

I only do a few hundred miles a year and use silicon brake fluid. Although the silicon fluid should not have any effect I wonder about lack of use or alternative sources of more durable components.

 

The failure is either high pedal pressure to obtain brake light function or total electrical failure.

 

Has anyone else experience of this regular failure ?

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I experienced once a failure of this switch (high pedal pressure needed to function) on my TR3 and replaced it by a switch on the brake pedal. I was installing a double brake circuit and the 4-way connector with the switch was deleted anyway.
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I use silicone brake fluid and have heard from many that this causes the problem.  My first hydraulic brake light switch lasted over 80,000 miles from new with DOT 3 fluid.  Since 1990 when I restored TRusty I have use silicone fluid and have had to replace it about every 3 years.  I connect an ohmmeter across the contacts and vary the air pressure from my air compressor to see if they work and at what pressure.  If about 30 psi, they work fine.  In 1996 I had to replace the switch  so I bought 2 of them.  Both tested OK at 30 psi.  Put one in and kept the 2nd in my spares.  Three years later, I had to use the spare one.  It wouldn't work - even at air pressure of 110 psi.  So I took it all apart and the 1/2" diameter copper plate that makes the contact was like a 20 year old penny.  It had tarnished.  No wonder it wouldn't make contact.  And it had never seen any silicone brake fluid.  These were all made by Intermodal in UK.

 

My spare now is a microswitch that I carry in my tool box and I install it on the brake pedal when needed.  Just 2 weeks ago, I installed another Intermodal switch not to lose originality points at the TRA National Meet in Ohio.  I came 2nd in my concours class with 86.1 points.  I have driven TRusty over 82,000 miles since 1990 and drove over 3400 miles this trip.  During the trip home I drove 794 miles in one day at an average of 67.6 mi/hr and got 33.54 mi/Imp. Gal. of petrol.

 

The switch still works.

 

Don Elliott, Original Owner, 1958 TR3A, Montreal, Canada

TR Register Member since 1987

http://www.zen21606.zen.co.uk/Forum%20Gallery/don3a2_big.jpg

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Thanks Don,

 

Your reply said what I suspected, i.e. the parts are poor. If the contacts had some either low corrosion copper (does it exist ?) or contact oil on the contacts then they would still work.

 

Even getting a few in for spares is the wrong answer, perhaps a visit to the scrap yard to source some off old Minis is the answer to obtain better quality parts.

 

Mine appear to be from a different manufacturer.

 

Regards,

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Jean - I have a bracket with a microswitch that I carry as my spare in my toolbox and which I can mount and connect in about 10 minutes when the original one becomes defective.  I like my TR3A to be as original as it can be for the US National Concours Meets.  I like to see how close I can come to the winners (usually recent restorations that in many cases are trailered there) - and I always take 2nd or 3rd in my TR3A class with about 86 to 90 points - and I have driven more than 82,000 miles (132,000 km) since I finished my restoration in 1990.

 

Don Elliott, 1958 TR3A - Even the owner/driver is the original one for this car.  I don't want to break the spirit or the spell.

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I re-routed the brake line away from the exhaust manifold and took away the switch as well. Brakelight is now switched over an MG (sorry guys) switch that is installed on the pedal box.

Reason to install this switch and not a TR part, was that I was not able to make partnr 134529 from Moss to switch in the "opposite" way, meaning on when out and of when in (pedal up and down) as it should. This switch comes on when pushed in and can therefore only be installed behind the brakepedal as in a TR6.

My problem is solved and works perfect (inspite of it bing from MG). Still interested to know what or if I did wrong with the TR one though?

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Don, that's fair enough and I have no objections. I have great respect for as person having his TR3 since new and caring for it since that date. My response was for less originality minded persons like me. So, bonne chance et beaucoup de plaisir avec les TRs.

Jean

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Brakelight is now switched over an MG (sorry guys) switch that is installed on the pedal box.

Rudi

Don't want to worry you but MGB's are plagued by aftermarket brake light switch problems as well, some owners have even got to the stage of using a relay to minimise the current going through the switch.

MGBs have two different switches, early ones were hydraulic and later ones worked off the pedal, both are equally useless, the consensus of opinion in the MG forums seems to be that the switch contacts get burned by carrying too much current, hence the relays.

I'm on my third switch in the last 4 years.

Ron

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