69 valiant electrical gremlin turn signal and license plate light

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sketch

sketch

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69 valiant. Here is current situation
  • license plate light does not work. I have swapped bulbs and nothing. Sand papered connection where bulb goes in; still nothing. I have heard about ground and using a test light but need guidance how to use it to check. It seems simple; clip ground and touch stuff but where to touch.
  • Front left turn indicator. When the headlights are off; indicator works as it should. when headlights are engaged, turn light stays lit orange and does not blink but inside the car the dashboard is showing that the blinker is working. Also, I have cleaned connections on ground wire. again, where would i use the test light to check where the ground short is?
  • I don't mean to sound stupid, but i have never worked on a car in my life but i am determined to learn. Thank you for any responses.
 
Make SURE you have the correct / compatible bulb. License lamp should be single contact

Both these sound like ground problems. The lic. lamp branches off from the tail light harness so first thing is make sure it is getting power. Make sure your test light is grounding. I use places like the trunk latch.

To test that a socket such as a parking light is grounding, think what happens.........the light gets power to the center pin, the current path is lamp bulb shell............to socket shell..........to ground.

If that path is broken, then wherever that break "is" the point will "at 12V" because the current has no where to go

So with lights on, and make sure that the lamp you are testing does have power on the wire, and that the bulb is good, Make certain your lamp is grounding, then probe the socket shell itself. Wiggle the bulb. If you get any glimmer of light while probing the socket shell, the socket is not grounding

Maybe the shell is grounding but the connection between bulb shell and socket is poort. With some lamp/ sockets, you can carefully probe and make contact on the bayonet pins. If you get a light there and not off the socket, then the bulb is simply not making contact with the socket.
 
sketch said:
using a test light but need guidance how to use it to check. It seems simple; clip ground and touch stuff but where to touch.
Click to expand...
The test light can show you if there is power getting to the lamp socket.

For example with one test lead clipped to a chassis ground, touch the other lead to the brass in the connector.
The tester should light up (when the parking lights are on).
If that works, remove the bulb and reconnect the socket and touch the other lead to the contact inside the socket.
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sketch said:
but inside the car the dashboard is showing that the blinker is working.
Click to expand...
Do you mean the dash indicator is blinking or on but not blinking?

sketch said:
Also, I have cleaned connections on ground wire. again, where would i use the test light to check where the ground short is?
Click to expand...

Not seeing evidence of a ground short.
A short is when two wires touch and the electricity finds a shorter path to ground through the wrong device.

A ground short is when a wire touches a ground and electricty takes the the shortest path to ground avoiding all devices.

sketch said:
I don't mean to sound stupid, but i have never worked on a car in my life but i am determined to learn. Thank you for any responses
Click to expand...

That's OK.
A few concepts will help get you grounded. Get it? grounded?
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When we talk about electricity taking the shortest path, we're talking about electrons flowing.
For that to happen there has to be a complete circuit back to the power source.
The power source when the car is running is the alternator. Otherwise its the battery.

The circuit must be completed for the electrons to flow.
If its completed with no resistance, LOTS of electrons will try to get from high voltage to low voltage. (actually they move the other way, but that's not important for our purposes) That's when the weakest part of the circuit gets hot and melts.

The amount of electrons moving is measured in amperes.
The energy level is measured in Volts.
 
Test light troubleshooting is correct. Then to confirm, use a jumper wire (with alligator clips, preferred) to "jump" from your device to a known good ground. If you previously had a bad ground, this will confirm it. It should now work.
 
using the test light as instructed; there is power to the socket. (license plate bulb) i tested it and the light comes on but when i put bulb in, nothing. brand new bulb pack, tried both bulbs and nothing. i even removed the part you have pictured and tested further up, there was light there too just no bulb lighting. I sanded out the hole again even though i was getting the test light to come on when touching. still nothing.
license plate light holder.jpg
ligh bulb.jpg
 
The socket must be grounded for the bulb to work. Test lights are grounded and will indicate voltage but when you install the bulb the housing must now be grounded.
 
Murray said:
The socket must be grounded for the bulb to work. Test lights are grounded and will indicate voltage but when you install the bulb the housing must now be grounded.
Click to expand...
suggestions for "grounding the housing?"
 
Plug the socket and bulb back in. Turn on the park lights. Attach a jumper wire from the socket (maybe through the bolt holes) to a place on the car body. This should be a convenient place nearby, maybe an old bolthole, bracket or the bumper itself. You may need to try different locations as paint, rust and dirt may interfere with grounding. The bulb should light if you have juice, a good bulb and a good ground. Good luck.
 
A wire with an alligator clip on both sides to jump the suspected gap.
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One of these or anything that can attach firmly to the body and the lamp housing.
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So after attaching if Light works that proves the lamp housing is bad? And then I need another one? Thanks Again.
Now on to the turn signal.
 
Depends what you attach the jumpers to.
The goal is to bridge the gap.
We don't know exactly where it is, just that its somewhere in the return.
You find it by sytematicly trying connecting different points in the ground path.
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Whatever you connected the test lamp to must be a good body ground.
So begin with connecting one end of the jumper to that.
Then connect or touch the other end to different parts of the lamp holder. See what happens.
 
okay. Going to get alligator clips.
Now for the turn signal. I took it off and used light tester on this. With headlights on the big hole registered light and when blinker activated the little hole also worked. But when blinker was off no light tester on small hole. This was consistent with issue of blinker not working when headlights are on. Blinker just stays lit. Where to hunt next?
F8D0E2F5-9637-4962-B108-614237247DA4.jpeg
 
What happened with the license plate light?
Never mind. I skipped your first sentance.
 
sketch said:
Now for the turn signal.
Click to expand...
Turn signals works. So the continuity test isn't going to show anything different.

One reason a turn signal will freeze is that one of the lamps in the circuit is out.
Question. Do any of you car's sidemarkers have lights in them? Also are there turn indicators on top of the fender.

The headlight relationship I'll need to think about but I suspect something is crossed or disconnected. Maybe a ground related to the instrument lamps panel.
 
So i took the passenger side light off and plugged in the suspect from the drivers side. The EXACT same thing happened. Headlights on no blinking but light stays on. when headlights are off; blinker works fine. I then plugged in the original passenger light again and it functions 100 percent correctly. Can the turn signal housing assembly go bad? it is weird to me since i could replicate it with moving it to the other side. deduction would say that the problem is in that assembly but there does not seem to be much to it. Could it be the bulb? i know crazy talk, but...
 
but the turn signal is now killing me. It fails on both passenger side and drivers side the same way. it seems like a simple device and yet,,,,
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Turn signal- I see two wires going to it. Are there two connecters on the bulb/ two filaments in the bulb? This means that your turn signal housing does two things- it is a park light and a turn signal (two things). This in turn means there is no third wire- a ground. These ground through the metal housing. Since most park lights are mounted in plastic grills (which insulates it) there must be some provision to ground the housing. Look closely at the wire loom.There must be a third wire to ground the housing. Both sides need to be grounded.
 
Mattax said:
Tell us what you did.
or as a famous radio personality of yesteryear would say.
"..and now for the rest of the story."
Click to expand...
My 15 year old said, "dad, isn't the bumper metal. Let's see what happens if we have the housing touch the bumper" Boom! Light came on.
 
Murray said:
Turn signal- I see two wires going to it. Are there two connecters on the bulb/ two filaments in the bulb? This means that your turn signal housing does two things- it is a park light and a turn signal (two things). This in turn means there is no third wire- a ground. These ground through the metal housing. Since most park lights are mounted in plastic grills (which insulates it) there must be some provision to ground the housing. Look closely at the wire loom.There must be a third wire to ground the housing. Both sides need to be grounded.
Click to expand...
Here is the crazy part. The passenger side works perfectly with the ground wire disconnected; in every situation. While the driver's side one will not come on for any reason if it is not ground

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So the electricity is finding another path to ground.
This almost certainly relates to why it doesn't work with the parking lights on.
With the lights off, current was flowing back through the parking light circuit.
Exactly to where I'm not sure. Maybe Murray or Redfish will know.
I always need to look at drawing for these circuits. I didn't want to do that until I knew if the car had any optional features.
 
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