In a message dated 97-10-08 06:58:08 EDT, jaltman@altlaw.com writes:
> What I don't understand is: If the indicator light finds its path to ground
> through the opposite side light, that means there is a current flow
through
> the opposite side light, why doesn't that light come on also? Is it that
> the current flow through the lil' indicator light is too little to
actually
> light the opposite side lamp?
Jim:
That is correct. A low wattage lamp, such as the indicator, has such a high
resistance, compared to the turn signal lamps, that the current through them
is too low to light the turn signal lamps, but is high enough light the
indicator. I don't have the exact numbers handy, but a turn signal bulb will
need about 3 - 4 amps, whereas the indicator will need only milli-amps.
Current flow through the series combination is detemined by the total,
combined, resistance. Compared to the indicator lamp resistance, the
resistance of the turn signal bulbs is nil. Thus, the current flow is
determined almost wholly by the indicator bulb.
This is a handy concept for applications such as this, but it can give you
fits when you are trying to do continuity checks. When I was using a test
lamp to test the just completed wiring in my TR6, I got the indication af a
short between two separate circuits. What was happening was, the current from
the battery in my test light was going through the switch in the first
circuit, through the light bulbs, through ground, through the light bulbs in
the other circuit, and back to the test lamp. The test lamp was not at full
brilliance, but close enough that it was hard to see the difference in a
lighted garage. The very low wattage bulb in the test light had a much, much,
higher resistance than the lights in the circuits under test. For a brief
moment, it was panicsville, till I looked at the schematic, and realized what
was going on.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74
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