All sidescreen TR's plus the early TR4's had a pressure switch that
activated when the hyraulic pressure in the brake line moved a small disc
forward to close a contact inside. In eleven summers sine I finished my
restoration (1987 - 1990) I have gone through 3 or 4 in 60,000 miles. Once
I even bought a spare and kept in in my tool box (just in case) tested it
(OK) and 4 years later when the one in the car failed, I put in my spare.
It failed after I installed it. I took it apart and found that the small
disc inside was made of copper. In the 4 years in my toolbox it had become
so tarnished (like an old penny) that the brown/black oxide prevented it
making contact. I returned it, put in the replacement and it has worked for
the last 6 months.
I test them in a vice with a continuity checker (ohmmeter) across the
terminals and apply air pressure with the gun from my air compressor. I
test them every 10 psi till there is enough pressure to make "contact" If
they take more than 30 psi to close, they won't work in the TR hydraulic
system.
I submitted a tech report on this to the supplier (TRF) and hopefully the UK
Manufacturer is making the inner discs now out of two cents worth of
stainless instead of a "Penny".
Also, you can use a later TR4 brake lamp switch that mounts onto the end of
the push-rod for your brake master cylinder.
Don Elliott, Original Owner 1958 TR3A
Montreal, Canada
P.S. With the fires you're having now in Aussie, you don't need brakes. I'd
get out of town as quick as I could.
----- Original Message -----
From: Michael Gajic <michaelgajic@hotmail.com>
To: <triumphs@autox.team.net>
Sent: Sunday, December 30, 2001 9:02 AM
Subject: TR4 Brake Light Switch
> Listers,
>
> My TR4's brake light switch has failed a mere 3 or so months after the
> fitting. It doesn't work at all, not even under heavy brake pedal
pressure.
> I have checked the wiring leading to/from it and it is fine.
>
> I believe that the heat from my TR4's extractors has fried the switch, a
> symptom that some of you have apparently experienced yourselves.
>
> Any suggestions on what to do to extract some reliability from my brake
> light switch? Is any particular supplier of TR4 brake light switches
> superior?
>
> Many thanks in advance,
> Michael
> 63' TR4
> Sydney, Australia
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