electrically stupid

I cannot quite remember what I'm supposed to be looking for. When the brake
is on, the tail lamp works, but if I turn on the headlights, the tail lamp
goes dark. Same thing happens when I hit the blinker. This only happens to
one light. The other one functions normally.

I cannot remember if I should be looking for a short to ground or a toaster
oven. Oh, and here's a good one. When the ignition is completely turned
off, if I turn on my wiper switch, it clicks, but my stereo system comes on.
Wow, what's that about?

No fuses blow, the light just goes dead. No matter what combination of
settings I try, only one filament in the bulb seems to work. The other one
never lights. (The bulb is good.)

Any ideas, because auto electrical really confuses me and gives me a good
day of screaming fits?

--
BDragon

BDragon wrote:
> I cannot quite remember what I'm supposed to be looking for. When the brake
> is on, the tail lamp works, but if I turn on the headlights, the tail lamp
> goes dark. Same thing happens when I hit the blinker. This only happens to
> one light. The other one functions normally.

Sounds like it could be a problem in the turn signal switch, or possibly
in the headlamp switch.

Do both the blinkers work with the headlights off, or just in one
direction? I'm not certain from your description, but I assume you are
saying all is normal with the headlights off, and one stop/blinker bulb
stops working when the headlights are on.

It is tough to diagnose an electrical problem from afar, especially when
we don't even know what model year you're talking about!
>
> I cannot remember if I should be looking for a short to ground or a toaster
> oven.

May just be an open circuit, since it affects both the stop light and
the turn signal... could be a corroded wiring harness pin or something
similar, but the fact that it works when the headlights are off seems to
me to point back at the two switches (turn signal and headlight switches).

Oh, and here's a good one. When the ignition is completely turned
> off, if I turn on my wiper switch, it clicks, but my stereo system comes on.
> Wow, what's that about?

Can't help without knowing what year Vette, or whether the stereo is the
stock setup or aftermarket (ie, has someone been mucking with the stereo
circuit?), or a wiring diagram.
>
> No fuses blow, the light just goes dead.
Are you back to talking about the tail light?

No matter what combination of
> settings I try, only one filament in the bulb seems to work. The other one
> never lights. (The bulb is good.)

"Never lights"? Don't you mean "never lights when the headlights are
on"? I assume you know "the bulb is good" because you've SEEN that
filament light up?

>
> Any ideas, because auto electrical really confuses me and gives me a good
> day of screaming fits?
>

If the bulb is good, then you need to start at the socket with a
multimeter, make sure you have a good ground at the socket, and with the
brake held on, trace the appropriate power wire back from there to see
what portion of the circuit that the power to that wire path is being
lost. That may require a wiring diagram for the car.

Or, take it to a competent electrical shop.

"WayneC" > wrote in message
...
> BDragon wrote:
> > I cannot quite remember what I'm supposed to be looking for. When the
brake
> > is on, the tail lamp works, but if I turn on the headlights, the tail
lamp
> > goes dark. Same thing happens when I hit the blinker. This only
happens to
> > one light. The other one functions normally.
>
> Sounds like it could be a problem in the turn signal switch, or possibly
> in the headlamp switch.
>
> Do both the blinkers work with the headlights off, or just in one
> direction? I'm not certain from your description, but I assume you are
> saying all is normal with the headlights off, and one stop/blinker bulb
> stops working when the headlights are on.
>
> It is tough to diagnose an electrical problem from afar, especially when
> we don't even know what model year you're talking about!
> >
> > I cannot remember if I should be looking for a short to ground or a
toaster
> > oven.
>
> May just be an open circuit, since it affects both the stop light and
> the turn signal... could be a corroded wiring harness pin or something
> similar, but the fact that it works when the headlights are off seems to
> me to point back at the two switches (turn signal and headlight switches).
>
> Oh, and here's a good one. When the ignition is completely turned
> > off, if I turn on my wiper switch, it clicks, but my stereo system comes
on.
> > Wow, what's that about?
>
> Can't help without knowing what year Vette, or whether the stereo is the
> stock setup or aftermarket (ie, has someone been mucking with the stereo
> circuit?), or a wiring diagram.
> >
> > No fuses blow, the light just goes dead.
> Are you back to talking about the tail light?
>
> No matter what combination of
> > settings I try, only one filament in the bulb seems to work. The other
one
> > never lights. (The bulb is good.)
>
> "Never lights"? Don't you mean "never lights when the headlights are
> on"? I assume you know "the bulb is good" because you've SEEN that
> filament light up?
>
> >
> > Any ideas, because auto electrical really confuses me and gives me a
good
> > day of screaming fits?
> >
>
> If the bulb is good, then you need to start at the socket with a
> multimeter, make sure you have a good ground at the socket, and with the
> brake held on, trace the appropriate power wire back from there to see
> what portion of the circuit that the power to that wire path is being
> lost. That may require a wiring diagram for the car.
>
> Or, take it to a competent electrical shop.
>
>
Sorry I didn't provide more detail. The car is a C3, 1977. The
combinations
that do weird things are these (all relative to the driver's side tail
light):
1. Headlights on:
A. as long as neither the brake nor blinker is activated, everything
appears normal
B. hit brakes, tail light goes out completely, re-lights when released
C. hit left blinker, tail light goes out completely, re-lights when
released
2. Brake pedal depressed, nothing else on:
A. light functions normally
B. turn on lights, tail light goes out, re-lights when headlights
released
C. hit left blinker, tail light goes out, re-lights when blinker
released
3. Hit left blinker, nothing else on:
A. tail light does not work

Regarding the filaments. There are two settings in which the tail light
works:
1. Headlights on, nothing else on, tail light burns the lower element.
2. Brake depressed, nothing else on, tail light burns the lower
element.
Aren't the running lights supposed to light one filament, and the brake
light
another? The same filament lights in both these cases. I have found no
condition where the upper filament lights.

I have the 1977 Corvette electrical manual. I haven't tested all the
possible
circuits because I keep getting dizzy, both from being confused and from
stuffing myself upside down under the dash.

I don't know if the wiper/stereo thing is connected to this light problem or
not.
I put the stereo in myself. I did not share either the hot lead, the
ignition lead,
nor the ground with any other device. I wired it in independently. That is
why
I cannot understand how the two effect each other. I bench tested the
wiper,
and it worked normally at both speeds, as well as when it parks. But when I
install it, and when I connect the ground wire to it, the stereo comes on.
The
wiper clicks when I turn it on, and when I change the speed setting, but it
does
not run.

I don't understand how the headlight circuit is involved either. It doesn't
share
a circuit with the brake circuit, or if it does, it's not supposed to is it?

Like your guess, mine so far has been the turn signal switch. Or maybe more
than one thing is happening. Because I could get it right away nearby, I
just
bought a new brake light switch. I'll start with that, but I don't think
that is
going to solve it. But, who knows?

If this gives you better information to take another guess from a distance,
please do so. I appreciate any help.

It's a bad ground. I'm willing to bet you're not looking at the taillight
filament when you press the brakes, just the brake filament that is not
any brighter than the taillight 'cause of the bad ground. There is a wire
that grounds to the frame. Crawl under the car (not sure *exactly* where
it's bolted 'cause it's been a couple decades since I've worked on one) &
find the ground wire running from the taillight to the frame. Unbolt it &
clean it & you'll have the lights working properly again.
Good luck with the wipers... ;^p
~ Paul
aka "Tha Driver"

Giggle Cream - it makes dessert *funny*!

Thanks for the idea. I had already done that, however, but thanks. I
welded up one of those do-dahs you can make with a caulk gun and I use that
to hold the brake down so I can go back to see what's going on. Sometimes,
I swear, I go stupid, however, and I'm going to check the filament again.
However, I only seem to get any juice through the one circuit. Inside the
bulb holder, you can see the two terminals easily, and one will give me
current, but the other doesn't. It baffles me, because it seems like that
means at certain times the running light uses that one circuit, and the next
test with another configuration and the brake light uses it. Does that make
any sense? Could the two supply leads be tangled out somewhere? Jeez, that
doesn't make any sense does it?

Oh, hell, I'm sorry. I top posted.

"ThaDriver" <imangeloneAThotmailDOTcom@> wrote in message
lkaboutautos.com...
> It's a bad ground. I'm willing to bet you're not looking at the taillight
> filament when you press the brakes, just the brake filament that is not
> any brighter than the taillight 'cause of the bad ground. There is a wire
> that grounds to the frame. Crawl under the car (not sure *exactly* where
> it's bolted 'cause it's been a couple decades since I've worked on one) &
> find the ground wire running from the taillight to the frame. Unbolt it &
> clean it & you'll have the lights working properly again.
> Good luck with the wipers... ;^p
> ~ Paul
> aka "Tha Driver"
>
> Giggle Cream - it makes dessert *funny*!
>

>Thanks for the idea. I had already done that, however, but thanks. I
welded up one of those do-dahs you can make with a caulk gun and I use
that
to hold the brake down so I can go back to see what's going on.
Sometimes,
I swear, I go stupid, however, and I'm going to check the filament again.
However, I only seem to get any juice through the one circuit. Inside
the
bulb holder, you can see the two terminals easily, and one will give me
current, but the other doesn't. It baffles me, because it seems like
that
means at certain times the running light uses that one circuit, and the
next
test with another configuration and the brake light uses it. Does that
make
any sense? Could the two supply leads be tangled out somewhere? Jeez,
that
doesn't make any sense does it?

>Oh, hell, I'm sorry. I top posted.
********
I use talkaboutautos.com to access these groups. I have to copy & paste in
the input box if I want the old message to show.
It's so hard to tell what's happening with wiring in person; impossible
over the web. Anything could be happening, but I don't think it's likely
the two leads are tangled. I *have* seen instances with these old GM
sockets with the buld installed 180 degrees off, causing all kinds of
wierd things to happen. You might consider replacing the socket if it's
corroded or hard to install the buld.
HTH,
~ Paul
aka "Tha Driver"

Giggle Cream - it makes dessert *funny*!

Thanks, Paul. It's even hard making some of this stuff in the daylight. I
guess I'll just poke around until I fry something or fix it. I think I'll
slowly replace the switches involved and hope a cheap one turns up to be the
problem first.
"ThaDriver" <imangeloneAThotmailDOTcom@> wrote in message
lkaboutautos.com...
> >Thanks for the idea. I had already done that, however, but thanks. I
> welded up one of those do-dahs you can make with a caulk gun and I use
> that
> to hold the brake down so I can go back to see what's going on.
> Sometimes,
> I swear, I go stupid, however, and I'm going to check the filament again.
> However, I only seem to get any juice through the one circuit. Inside
> the
> bulb holder, you can see the two terminals easily, and one will give me
> current, but the other doesn't. It baffles me, because it seems like
> that
> means at certain times the running light uses that one circuit, and the
> next
> test with another configuration and the brake light uses it. Does that
> make
> any sense? Could the two supply leads be tangled out somewhere? Jeez,
> that
> doesn't make any sense does it?
>
> >Oh, hell, I'm sorry. I top posted.
> ********
> I use talkaboutautos.com to access these groups. I have to copy & paste in
> the input box if I want the old message to show.
> It's so hard to tell what's happening with wiring in person; impossible
> over the web. Anything could be happening, but I don't think it's likely
> the two leads are tangled. I *have* seen instances with these old GM
> sockets with the buld installed 180 degrees off, causing all kinds of
> wierd things to happen. You might consider replacing the socket if it's
> corroded or hard to install the buld.
> HTH,
> ~ Paul
> aka "Tha Driver"
>
> Giggle Cream - it makes dessert *funny*!
>
>

With a witness to make sure I didn't screw it up, I can verify that no
matter which switch is on - headlight, brake, or blinker - the same one
filament in the bulb is the only one that lights. How is that possible?

"BDragon"

>With a witness to make sure I didn't screw it up, I can verify that no
matter which switch is on - headlight, brake, or blinker - the same one
filament in the bulb is the only one that lights. How is that possible?
***********
Then it has to be in the wiring. The tail & stop lights are two different
circuits; I don't see any way a switch could cause this. Verify one more
time using a 12 v. test light that it's the same part of the *socket*
being fed by both the light switch & the brake light/turn signal switches.
If so you'll have to start tracing the wiring using the test light to
determine where the problem is. Trace back from the taillight; start by
unplugging the taillight socket & test the plug. If it's still the same
wire being fed there, determine where that wire goes to inside the car &
test there, etc. etc.
~ Paul
aka "Tha Driver"

Giggle Cream - it makes dessert *funny*!

I'm not an expert on anything but I think you're going to find it's a bad
ground causing a feedback.
I've had a similiar experience of the lights not operating correctly and it
all came down to the ground
wire for the brake light socket.

"ThaDriver" <imangeloneAThotmailDOTcom@> wrote in message
lkaboutautos.com...
> >With a witness to make sure I didn't screw it up, I can verify that no
> matter which switch is on - headlight, brake, or blinker - the same one
> filament in the bulb is the only one that lights. How is that possible?
> ***********
> Then it has to be in the wiring. The tail & stop lights are two different
> circuits; I don't see any way a switch could cause this. Verify one more
> time using a 12 v. test light that it's the same part of the *socket*
> being fed by both the light switch & the brake light/turn signal switches.
> If so you'll have to start tracing the wiring using the test light to
> determine where the problem is. Trace back from the taillight; start by
> unplugging the taillight socket & test the plug. If it's still the same
> wire being fed there, determine where that wire goes to inside the car &
> test there, etc. etc.
> ~ Paul
> aka "Tha Driver"
>
> Giggle Cream - it makes dessert *funny*!
>