Nissan Altima: Blinking Headlights in 1996 Nissan Altima GXE

> I have a 1996 Nissan Altima GXE. Recently I have observed that, after 

Hi Sateesh

I've never seen that before.

Are you sure _all_ lights (head lights, turn lights, brake lights,
plate lights, etc) go out? Perhaps make sure because there are some
fuses and feeds common to some lamps but not to all, as far as I can
see on the schematic.

When it happens again, perhaps press down on all fuses and fuseable
links in the fuse box under the hood to see if it the problem changes.
Maybe you just have a bad contact in that area.

Hope you find it soon.
Remco

I did check all the fuses. They seem to be fine. Also last week, I got
my battery replaced and I was told by Sears that alternator is fine. I
thought it would go away with battery replacement as the old battery
voltage was 10.55V on load. Unfortunately the problem still exists.

BTW.. I am sure that it is happening with headlights (in both
positions), dash board lights, overhead lamp (inside the car). They do
not go out completely but the effect is as if the voltage passing to
them is up and down.

Could not check turn lights and stop lights.

Sateesh

remcow wrote: 
after 
and 
but 
are 
of 
changes. 

Hi Sateesh

Ok, the lights dimming is definitely a clue. Initially you mentioned
they 'blink', suggesting they actually turn off. Dimming means that
either the path to the lights has a higher resistance than normal or
that something draws a lot more current than normal.

I'd check the power connections to the battery first - make sure that
the wires are secured at both ends. Take the wires off the terminal and
clean them with some sand paper.
Also check all ground wires to the chassis and engine - I suspect one
is not making good contact.

With the car running and everything on, measure the voltage on the
battery. Under full load, it should be about 14V if the battery is
charged. If you see any less, clean the wire from the alternator on
both sides.

Hope you get it solved soon.
Remco

Hi Remco,

Thanks for your inputs.

I have got the battery replaced 3 days back by Sears Auto Center. The
wires are secured and they are fine. After replacement, on load the
voltage is 15V. So I guess that is also ruled out. Only thing that is
left over is, checking the grounding. How do I check that?

BTW.. I didn't understand what do you mean by saying "Dimming means
that
either the path to the lights has a higher resistance than normal".

If some path has higher resistance, then the volatage on the end is
continuously lower than the normal (or stable). It will not have
dimming effect. But, in my case, it becomes bright and then normal (it
was hard to find out whether dimming effect is, normal to bright to
normal or normal to dim to normal). Does it mean it is some kind of
variable resistance?

Reards,
Sateesh


com wrote: 
and 

Hi Sateesh

Resistance is a property all wires have -- the thicker the wire, the
less resistance.

Not knowing how much you know about electricity, compare wires to water
pipe and voltage to water pressure.
If you try to push a lot of water through a thin pipe, it will not all
want to all go through it very quickly. This means low flow, high water
resistance and high potential pressure. In other words: low electrical
current, high resistance, high voltage across the wire.
Conversely, if the pipe is very wide, a lot of water can go through it.
High flow, low water resistance, and low potential pressure. In other
words: high current, low resistance, low voltage potential across the
wire.

What can happen is that a path to those lights is going through the
equivalent of a thin pipe -- a wire that migh not make good contact.
This wire has a high resistance and thus only allows some current to
flow to the lamps.
Since your lamps require a lot more current than can be supplied
through those wires, they dim.

The way to check that is to put a volt meter across your battery while
the car is running and all your lights are on. You'll see a voltage of
around 14V. You move the positive lead to the fuse box but keep the
negative lead on the battery. You should still see around 14V -- if you
don't, the wire that is in place between the fuse box and the battery
has most likely a high resistance and should be cleaned. If you do see
14V, you move the negative lead to the chassis and check for 14V. If
you don't see 14V, the negative lead between the battery and the
chassis has high resistance and should be cleaned. You basically "walk"
these probes towards the offending light and should be able to
determine what path has a high resistance. It can be time consuming and
you basically need to have a decent understanding of where your wires
are going.

Another way is to just clean all contacts (battery, chassis, engine).
Make sure to tighten them all down properly after cleaning.

Electrical problems can be a pain to find. Most of the time it is a bad
contact on a ground lead because they tend to be exposed to the
elements.
Hope this helps.

Remco

Hey Sateesh.

Just one more bit: right -- the wire may not really have a variable
resistance. You'd see arcs all over the place. I'd certainly hope not


The problem is that multiple devices find their way to ground across a
wire that might just be meant for one device.
After reading your comment a little more, I see you do understand
electricity so the current through this wire is more than normal.
The more current through a wire, the more voltage across that wire so
less voltage gets to your intended device.

Ohms law is E=IR. (voltage = current * resistance)

For instance, let's say your lamp draws 5 Amps. One leg's resistance
(let's say ground) is .5 ohms - let's assume there isn't any resistance
in the other leg (doesn't happen, but will make the calculation a lot
easier to understand)

The voltage across that wire will be 5(current) * 0.5(resistance) = 2.5
V. So the voltage that your lamp gets at best is 14V(running voltage) -
2.5V(voltage drop on wire) = 11.5V.

Now let's say that for whatever reason (maybe a bad ground) the radio
also finds its ground through this path. Assume it draws 4Amps. Total
current through this wire is now 5 + 4 = 9 Amps. The resistance hasn't
changed but the voltage across that wire has changed : 9 * 0.5 = 4.5V
-- so the voltage to your device changes too: 14V - 4.5 V = 9.5V.
Perhaps the device that finds this ground is not a radio, but something
that intermittently uses power (maybe a cooling fan) -- you see the
point: the lamp will dim when the fan goes on.

I explained electricity in terms of water flow in my previous post
because I wasn't sure what you understood when it came to electicity.
Please understand I did not mean to patronize you, just make the
information understandable.
Hope this helps -- "good hunting" finding the problem.
Remco

Hi Remco,

I could not trace the problem. Now I have more reasons to believe that
the problem is somewhere else.. Since two days, the fluctuation
worsened (if you remember from my previous posts, headlights dim
according to the tachometer flucutation. Now the tachometer fluctuates
between 0 and 1000 rpm and soemtimes car engine stops completely.. Have
to wait for 5 minutes to start the engine and wait for the tachometer
to stabilize (by keepking leg on gas for couple of minutes) and then
move the car.. I guess it is time now to take the car to a mechanic.
:-)

Any clue what could be the problem..

Regards,
Sateesh



com wrote: 
a 
resistance 
2.5 
- 
hasn't 
something 

> 

Hi Sateesh

Sorry to hear that you didn't find it yet.
This almost seems like a different problem because originally didn't just
your headlight dim once on a while?

The light dimming / engine dropping in RPM could mean several things. It
could be that the RPM is dropping due to the voltage on the battery dropping
more than normal. Of course, the voltage across the battery also could drop
because the engine RPM drops -- one could be the effect of the other and
vice versa. (another adaptation of what came first: the chicken or the egg

To isolate the actual cause could be tricky.

I'd make sure that your alternator maintains a decent voltage (should be
around 14V or so) across the battery's terminals when running at constant
speed first -- you may need to put your foot on the accelerator to maintain
a certain speed.

Regards,
Remco