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Re: Electrical Theory

To: "Rick Huber" <>, "Fred Pixley" <>
Subject: Re: Electrical Theory
From: "Paul Hunt" <>
Date: Sat, 15 May 1999 17:51:06 +0100
Never mix water and electricity


-----Original Message-----
From: Rick Huber <>
To: Fred Pixley <>
Cc: mgs-digest list <>
Date: 04 May 1999 23:45
Subject: Re: Electrical Theory

>Fred and others,
>Since I started this brake switch is hot thread, I thought I'd throw my
>2 cents in.
>In my tiny mind I understand it this way.  Voltage is like the pressure
>of water in a pipe and current is like the flow of water through the
>pipe.  Resistance to flow causes pressure drop, roughly equivalent to
>power.  With the system energized with the 12 volt battery to an open
>switch, there is pressure, or 12 volts available to the switch, but no
>current flow, like pressure up to a spray nozzle on the hose.  Once the
>switch is closed, when you press the brake pedal, 12 volts is available
>to the light bulb.  If the ground past the bulb is open, i.e. not
>grounded, then there is 12 volts available through the whole circuit,
>but still no current flow.  Once the ground past the bulb is closed, as
>much current flows through the system as the element in the bulb will
>allow (it's the orifice or the spray nozzle on the hose), so the element
>is like an orifice in a pipe.  12 volts upstream, current flow of a
>couple of amps through the element,  producing power and therefore light
>and heat, and then much lower voltage on the downstream side of the bulb
>back to ground.
>As has been said already, normally, there is essentially no resistance
>anywhere in the circuit except at the light bulb element.  However, when
>the contacts in the switch become corroded over 24 years, they become
>the resistance in the circuit more than the elements in the bulb, so the
>power is taken across the contacts in the switch and it gets hot.
>Downstream of this orifice, there's not enough voltage left to light the
>bulbs.  The analogy here is a kink in the hose upstream of the nozzle,
>therefore no flow through the nozzle when it's open.
>So what I did was take the switch apart, clean the contacts very
>thoroughly (remove the kink in the hose), and now I have brake lights
>It seems so simple now trying to explain it, why couldn't I figure it
>our this easily when I was troubleshooting?
>Safety Fast,
>Rick Huber
>75 V8 B Daily Driver
>65 B undergoing lengthy restoration

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