DANMAS@aol.com wrote:
>
> In a message dated 97-03-12 16:31:59 EST, you write:
>
> << Dan, sorry but I must differ with you. My TR4 ammeter does not have any
> LARGE cable running to it and it does not register when the ignition is
> turned off. This is the original configuration. Maybe a check of the wiring
> diagrams in Haynes or Bentley will show why. I'll check tonight. >>
>
> I guess LARGE is a relative term, but when you consider that the entire
> electrical load of the car, with the exception of the horns and starter on
> TR2 thru 4A, and horns, starter, courtesy light and high beam flasher on the
> TR6, pass through the ammeter, I would think a large cable would be required.
As I recall, there were only two fuses (and an in-line fuse for the
horns sometimes) on a great number of British sports makes (which always
made me think that the little label on the fuse box cover should have
read "LIGHTS --- ALL BLOODY ELSE" <g>). If I were to mentally add up
all the steady-state loads on a bare-bones roadster of `50s-`60s
vintage, it probably wouldn't be more than 25 amps, and Lucas probably
figured (often wrongly) that any wire could handle the intermittent
loads without failure. And if the wire runs were short enough, a 10 ga.
ammeter wire could probably handle 25A dc without exceeding the
insulation temperature rating. If one adds in 5-6 amps for a heater
blower motor, then 10 ga. was likely on the ragged edge. But then,
that's what Lucas probably thought was okay. <g> At any rate, the
overall loads probably couldn't exceed 25 amps, since the maximum
generator output (according to my TR4 factory manual) is 22 amps. BTW,
this encourages a question--was Lucas the OEM manufacturer of electrical
harnesses for the British car industry, or did they simply supply
equipment?
> One thing I have found from working on my Triumphs and MGs is that the
> factory tended to use cables that are at least one size smaller that
> Electrical Engineering standards call for. For example, I had the main power
> feed on my TR6 burn in two at the ammeter at 70 mph on the interstate at
> night (a scary experience!!!). When I replaced it, I found the factory cable
> to be a 28 strand conductor, rated at 17.5 amp. To handle the alternator
> output, it should have been a 65 strand conductor, rated at 35 amp. Needless
> to say, I replaced it with a 65 strand conductor.
Somehow, this doesn't surprise me at all... what may have started out as
a necessity due to material shortages after WWII may have become
ingrained in the industry as standard practice after enough time.
> Wiring, my source of British wiring supplies. Are there other sizeing schemes
> used by the Brits? If anyone knows, please let me know.
Not sure if they've always been available to the Brits, but a great many
wire suppliers and manufacturers world-wide are now using metric wire
sizes, much like the Germans have been using for years. I think GM now
uses metric wire sizes exclusively, and we've been using them on an
ex-GM product for 6-7 years now. Wouldn't surprise me if recent British
makes are using such now.
> I would be very curious as to the size wire you find on your TR4. I know it
> will be impossible to tell for sure from looking - anyone know for sure?
Memory fades after about twenty years, but I thought the one on my TR4
was roughly 10 ga. Even the original factory manual has only a
description of the harness and nothing whatever about wire sizes.
Cheers, Dan.
--
My other Triumph doesn't run, either....
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