Both low beam headlights out

#11

"SnoMan" <admin (AT) snoman (DOT) com> wrote

Quote:

On Sun, 20 May 2007 16:34:01 GMT, "Jeff Strickland"
crwlr (AT) verizon (DOT) net> wrote:

Only the Low Beams have failed, and there are only two of them. I would
not
suspect a voltage regulator at this time.

That depends because low beams are used the most and would suffer
first from over voltage. It only takes a few seconds to check voltage.

Okay. I would not waste my time or suggest that anybody else waste theirs.

I suspect that one headlamp simply failed due to age, and the operator
either failed to notice, or did notice but took no action. After an unknown
period of time, the other lamp failed due to age.

PS
Anytime the low beams are on, all of the other lamps are also on, so to
suggest that the low beams are used more is inaccurate. They are used more
than the high beams, that much is true.

#12

"David M" <NOSPAM (AT) nospam (DOT) com> wrote

Quote:

On Sun, 20 May 2007 16:41:49 +0000, Jeff Strickland rearranged some
electrons to form:

"lugnut" <lugnut (AT) roadkill (DOT) net> wrote in message
news:96c053hhlec4hg162botu06io016e6gp3t (AT) 4ax (DOT) com...
On Sat, 19 May 2007 18:50:31 GMT, "sf/gf" <sf90006 (AT) kart (DOT) com
wrote:

Vehicle is a 93 Ford Ranger. My son visited me yesterday and mentioned
that
one of his headlights was out. Upon observing, I noted that both low
beams
were out. I removed one headlight bulb and sure enough, one of the
filiments is broken. My son swears that he had one low beam working
just
the night before. I suspect a wiring problem since the odds of BOTH low
beams failing within 24 hours are very high. However, both of the high
beams work ok. That leads me to believe that maybe the wiring and
switch
is
ok. Turn signals, stop lights and parking lights work ok. If I replace
both headlight bulbs and both of the low beam filiments blow, where
should
I
start looking as to a short circuit? By the way, I checked the fuse box
under the hood and could not find any headlight relay. Is there one?
Does
the Ford have a built in circuit breaker in the headlight switch as do
most
other vehicles?

It is a quite normal occurance after one lamp fails. Once
you have one lamp failed, the other will usually have a bit
more voltage available

Say what!?

My house has vlotage coming in from the nearest transformer. If I unplug
EVERYTHING except for one night light, the light is still only going to
get
110 and draw the amperage it requires. It will not get blasted with all
of
the voltage and current coming into the house. A motor vehicle works the
same way -- the alternator produces whatever it produces, and any given
load
takes what it needs. If there are too many loads, then the voltage
produced
will drop, but there is no way that any given load will be over-supplied.

Not exactly. An automotive power system is a lot 'softer' than a large
AC distribution system, meaning that it is more sensitive to load changes.

Try this experiment: Put your analog voltmeter on the battery while the
alternator is turning. Turn on all the electrical loads in the
car...headlights and A/C blowers in particular. Have an assistant
switch off the loads. As each one is switched off, you will see the
voltmeter needle jump up, and then settle back. (A cheap Radio
Shack digital voltmeter will likely not respond quickly enough to
show this).

The alternator voltage regulator does not respond instantaneously to a
change in load.

Any electrical circuit (even a piece of wire) will have some small amount
of inductance. Voltage across an inductance is equal to the inductance
multiplied by the time rate of change of the current through the circuit.
( V = L * di/dt). Turning a circuit on or off causes the current to
change rapidly in a short time (therefore di/dt is large).

Not quite sure what you meant by:
It will not get blasted with all of
the voltage and current coming into the house.

All of the circuits are in parallel, therefore they all see the same
voltage that comes into the house, no matter how many are turned on or
off. But as things are turned on and off, the exact same phemomenon as
described above (switching transients) are also generated in your house.

I sometimes explain electricity to people who don't understand it
as follows:

Think of the conductor as a water hose. The voltage is the pressure in
the hose, and the water flow is the current. If you switch off the
nozzle, the pressure (voltage) is present in the hose, but no water
(current) is flowing.

I know all of that.

My analogy still holds true. The time it takes for the automotive system to
adjust itself is not long enough hurt anything.

#13

"David M" <NOSPAM (AT) nospam (DOT) com> wrote

Quote:

On Sun, 20 May 2007 21:42:34 +0000, Jeff Strickland rearranged some
electrons to form:

Say what!?

My house has vlotage coming in from the nearest transformer. If I
unplug
EVERYTHING except for one night light, the light is still only going to
get
110 and draw the amperage it requires. It will not get blasted with all
of
the voltage and current coming into the house. A motor vehicle works
the
same way -- the alternator produces whatever it produces, and any given
load
takes what it needs. If there are too many loads, then the voltage
produced
will drop, but there is no way that any given load will be
over-supplied.

Not exactly. An automotive power system is a lot 'softer' than a large
AC distribution system, meaning that it is more sensitive to load
changes.

Try this experiment: Put your analog voltmeter on the battery while the
alternator is turning. Turn on all the electrical loads in the
car...headlights and A/C blowers in particular. Have an assistant
switch off the loads. As each one is switched off, you will see the
voltmeter needle jump up, and then settle back. (A cheap Radio
Shack digital voltmeter will likely not respond quickly enough to
show this).

The alternator voltage regulator does not respond instantaneously to a
change in load.

Any electrical circuit (even a piece of wire) will have some small
amount
of inductance. Voltage across an inductance is equal to the inductance
multiplied by the time rate of change of the current through the
circuit.
( V = L * di/dt). Turning a circuit on or off causes the current to
change rapidly in a short time (therefore di/dt is large).

Not quite sure what you meant by:
It will not get blasted with all of
the voltage and current coming into the house.

All of the circuits are in parallel, therefore they all see the same
voltage that comes into the house, no matter how many are turned on or
off. But as things are turned on and off, the exact same phemomenon as
described above (switching transients) are also generated in your house.

I sometimes explain electricity to people who don't understand it
as follows:

Think of the conductor as a water hose. The voltage is the pressure in
the hose, and the water flow is the current. If you switch off the
nozzle, the pressure (voltage) is present in the hose, but no water
(current) is flowing.

I know all of that.

My analogy still holds true. The time it takes for the automotive system
to
adjust itself is not long enough hurt anything.

Although it's not likely that transients burned out the OP's
headlights, your AC distribution analogy still has some problems, or
maybe you don't have a good understanding of basic electrical circuits.

In fact, the circuits in your house will 'get blasted with all of the
voltage' (to use your words), since they are parallel circuits.

As I stated before, an AC distribution system (at least in the US) is
usually pretty stiff, meaning the voltage changes very little with load
changes. In other countries, especially developing countries, this is not
always the case. In a place that I worked (not in this country) a
couple of years ago, the local AC system was so soft that there was not
enough fault current available to trip even a relatively small circuit
breaker in the presence of a conductor-to-ground fault (the voltage
dropped instead).

Automotive systems are also parallel circuits.

You are splitting hairs. There is never a problem with one headlamp getting
"too much power" because the other one has burned out.

I get that my analogy is not accurate for every instance, but it is more
than adequate for the topic that is being discussed by everybody but you.

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Both low beam headlights out

Ford Trucks Ford Trucks (alt.trucks.ford)

Re: Re: Re: Both low beam headlights out - 05-20-2007 , 04:39 PM

Re: Both low beam headlights out - 05-20-2007 , 04:42 PM

Re: Both low beam headlights out - 05-20-2007 , 09:13 PM