A test light needs a battery.
It is used to test for a complete circuit.
If the fuse is good the test light will glow.
A good ground will make the test lamp glow any time you go metal to
metal(unless the metal is not touching the car frame.".
Well, I guess there is more than one type of "test light."
A common one used for trouble shooting automobile wiring looks like
screwdriver handle with a ice pick tip. There is a wire lead with a
allegator clamp that is supposed to be connected to a metal part of the
chassis (with today's plastic cars, it can be difficult to find metal in the
passenger compartment or even the trunk) There is a 12 volt lamp in the
handle. With the lead connected to "ground" (the metal chassis) you poke
about with the ice pick point to see where power is and where it ain't.
Many automotive fuse holders do have any "hot" metal exposed which makes
things safter but it requires you to "dig in" with the ice pick to see
whether the fuse is working. The ice pick can also punch a hole in a wire
to see if the conductor inside is "hot."
For household use there is the neon "tester" which is just a small neon lamp
in series with a resistor. If you connect the two leads to 120 volts the
lamp will glow brightly. If you hold one lead in your hand, you can use
the other lead to test for "hots." When the other lead touches a hot wire,
the lamp will have a dim glow.
With the "testers" with batteries, the simplest would be a continuity
tester. It's like the ice pick test except that it has a 1.5 volt bulb and
a 1.5 battery. If the lead touches the tip the lamp will light. It's
useful for simple testing of stuff that out of the car or when the battery
is disconnected. With power on, you risk turning the 1.5 volt lamp into a
There are small testers with batteries that can sense AC voltage and can
also function as continuity testers. One side of the circuit is through
the body of the user. These are nearly impossible to burn out and are
handy to keep in your "junk drawer."
On 11 Sep 2004 22:45:09 GMT, firstname.lastname@example.org (USApoSOUL) wrote:
If this is one of the simple test lights with a lead coming off what
looks like a screwdriver and a light in the handle, connect the lead
to a ground in the car. This would be a screw or other piece of metal
somewhere in the vicinity of where you are looking for a voltage to
You can check to see if you do have a good ground by checking a point
on the fuse block that has voltage. If the light works, you have a
good ground and can check other points to verify if a fuse is good.
You of course have to leave the fuse plugged in the fuse block to
check them with this light. A good fuse would check with a light on
both sides if good.
Only one side would light if the fuse is bad.
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