RE: 74 GTV brake light switch

[Dana Loomis <dloomis@domain.elided>]

In AD V8#674  bubonic@domain.elided  aka Kelly M  enquired:
>
>Can someone please explain the operation of the brake light switch for a
>>74 GTV.  I am having intermittent brake light problems.
>>
>>I have 12 + volts on one side of the switch and Aero volts on the other,
>>when I push on the pedal, the 12+ volt side drops to zero and the lights
>>do not work.  Is this how it should work?
>
>To which I replied:
>
>Yes, exactly.  Pushing the pedal down closes the circuit, so there is no
>voltage differential across the switch.

Then John Fielding said: 

>I don't think you are answering the question correctly!  You both seem to be
>talking at cross purposes.
>
>With the 12V on one side of the switch with the brake pedal not pressed you
>should see zero volts on the other side - the side which connects to the
>lights.  However, when the brake is pressed the 12V on the battery side
>should remain 12V and the other side should now also show 12V, and the lamps
>should be on.

My response to all of this: 

Perhaps all of us are confused about what the original post, which  I've
lost track of, said.  My interpretation was that the poster was measuring
the voltage across the terminals of the switch.  John's description would
be consistent with proper operation of the switch if the voltage were
measured from each terminal to ground.

Dana

Dana
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