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Simple electrical question from a rookie
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mactube
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Dec 17, 2022, 5:25 PM
Post #1 of 20
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Simple electrical question from a rookie
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I want to fix my trunk light on my 2016 Hyundai Elantra. Since it stopped working , I thought it was a simple fix like the fuse or the bulb, but it wasn’t so I checked the power going into the assembly with a multimeter. The power off goes into the assembly At 10.5 V when the car is off. Now to my question: When I Put the light bulb in and check the power again it’s at 0 ! Try it the same with another lightbulb and check the power at the plus and minus pole and it stays at 0 . Is that normal or is that why the light is not working? Check out the pick: https://drive.google.com/file/d/1Fw_Nw8JgKiQ0qBnrWCerouvxNxQ8Xmol/view?usp=sharing
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Hammer Time
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Dec 17, 2022, 5:34 PM
Post #2 of 20
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Re: Simple electrical question from a rookie
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The video is not accessible without logging in so I can't watch it.
You can't test the voltage if the light is on. The light socket likely had a mercury switch built in so it shuts off when the trunk is closed. Just test for power at the base of the socket with the bulb removed, preferably with the engine running.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Dec 17, 2022, 11:29 PM
Post #3 of 20
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Re: Simple electrical question from a rookie
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Those sockets are usually the switch (mercury as Hammer said) right there. Does it unplug there too? Try that it could be the switch.
Mercury not used anymore but same idea makes the connection when tilted then OFF when closed or at a certain angle.
This is pretty new to fail but they do be glad it's off or can have a dead battery over that stuff,
T
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mactube
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Dec 18, 2022, 4:49 PM
Post #4 of 20
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Re: Simple electrical question from a rookie
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OK sorry , here is the link to the picture:
https://drive.google.com/file/d/1Fw_Nw8JgKiQ0qBnrWCerouvxNxQ8Xmol/view?usp=sharing
It shows me testing the power at the two poles of the assembly at 0 but when the bulb is removed in the same position it shows 10... Volts with engine running 13 V
at the end of the clear light cover is the little black socket which also reads 10 V when I connect the Multimeter directly in there. Just when I put that , or another light bulb in there it will show 0 Volts
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mactube
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Dec 18, 2022, 4:51 PM
Post #5 of 20
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Re: Simple electrical question from a rookie
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I haven't even looked for the switch yet, because when the trunk lid is open the power will go the socked / assembly. Just when the light bulb is in there it goes to 0.
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Hammer Time
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Dec 18, 2022, 4:53 PM
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Re: Simple electrical question from a rookie
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That picture shows you with a probe at both ends of the bulb. What are you expecting to find there?
If you are testing for voltage attach the black lead to ground somewhere and use the red lead to test.
It's starting to look like you just have a bad bulb.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Dec 18, 2022, 4:55 PM)
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Tom Greenleaf
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Dec 18, 2022, 5:58 PM
Post #7 of 20
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Re: Simple electrical question from a rookie
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The end of the game is bulb wants FULL power and ground. It's there in wait so this isn't rocket science, find where it lost it.
Bulbs, thanks China, have a high failure rate a blow one usually looks black smoke inside. Recent redo, whole vehicle 1/2 blew right away, one throwing fits right now just erratic?? Damn cheap junk!
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It's off this topic for you but I take all those bulbs out of my own fleet of cars BC that crap causes problems note most are over 20-30 years old same ideas. Yup, park on a hill/slope find dead car - screw that.
Those with switches (might be yours!!) don't do that.
Dollar store have 2 flashlights for a $US buck. WTF are we messing with?
Tom
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mactube
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Dec 19, 2022, 8:52 PM
Post #8 of 20
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Re: Simple electrical question from a rookie
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Sorry it was a little hard to hold the stuff and take the pic, but the tester is connected to ground / pole ( copper metal part on the top and the + at the lower metal part of the assembly which the bulb sits in. If I leave the tester right there in the same position, and take the bulb out, its at 10 V once I put the NEW bulb in or the old one it shows 0.
I get 10V at the connector and all the way to the end of the metal parts that hold the bulb , but once the bulb is in .. no voltage but its a new bulb and same with the old one. You can see the assembly a little better on the picture of this link : https://drive.google.com/file/d/13wP-0p-yhrdRbKU7mI1u8M_BtnIKuHX2/view?usp=sharing
So my question is, does the bulb take a way voltage from the poles ?
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mactube
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Dec 19, 2022, 9:12 PM
Post #9 of 20
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Re: Simple electrical question from a rookie
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The old bulb doesn't look blown but I still tried 3 different ones out of a new pack.
The Volt disappears once any light bulb is in the assembly.
I'm trying to find where the power is lost .. but its good all the way from the connector, to the tip of the metal parts that hold the bulb then once the bulb its in .. no more Voltage ..
https://drive.google.com/file/d/13wP-0p-yhrdRbKU7mI1u8M_BtnIKuHX2/view?usp=sharing
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mactube
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Dec 19, 2022, 9:16 PM
Post #10 of 20
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Re: Simple electrical question from a rookie
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Since power is good without the assembly in it and I already have new bulbs, I would just buy a new assembly , but
That's literally a plastic cover with the two metal poles in there which can't be broken and the tester show power there.
So the question is ... why does the Voltage magically disappear when I put the light bulb in ?
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Tom Greenleaf
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Dec 20, 2022, 2:42 AM
Post #11 of 20
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Re: Simple electrical question from a rookie
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IDK why your results. Just use a dang test light but the bulb test has me thinking the wire to, plug nearest to this plucking thing is on hair of wire.
It it's powered thru bending wire that's common for those to break.
If dots that touch when closed types will cause hair loss put pennies on some just said another thread/person.
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Of the best cars I ever owned 1963 didn't have a radio, back up lights?? What for use the braille method (OMG) so never a problem, nothing to go wrong :-) --------------- you got where you were going and back we've lost the whole point of things!
Tom
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Hammer Time
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Dec 20, 2022, 4:48 AM
Post #12 of 20
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Re: Simple electrical question from a rookie
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Again, you are testing it wrong.
Your black cable needs to be connected to a solid body ground. That lamp is not grounded when you are holding it in your hand. You are relying on the return wire of the ground and that could actually be your problem. Use an actual ground to test for power.
Yes when the bulb is in it is consuming all the available voltage so test it properly and see what the real amount of voltage is. Then we will know if we have a voltage problem or a ground problem.
Do other interior lamps work properly?
As you can see, this circuit is not so simple.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Dec 20, 2022, 5:01 AM)
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mactube
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Dec 21, 2022, 4:30 PM
Post #13 of 20
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Re: Simple electrical question from a rookie
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OK great thanks ! Yes looks a lot more complicated the I I thought it was..
All other interior lights work .
I will be back with results from proper ground testing !
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Tom Greenleaf
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Dec 21, 2022, 5:04 PM
Post #14 of 20
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Re: Simple electrical question from a rookie
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Basics: Items that use 12V either get grounded to work or power.
An incandescent (not LED both are handy) uses some power vs LED.
Reverse the common ones (dirt cheap) power the wire to test grounded things and ground it to test positive power. Takes both or nothing works.
Hope that helps the problem is usually a dumb wire busted even inside insulation makes it harder to pin down,
T
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Hammer Time
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Dec 21, 2022, 5:37 PM
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Tom's idea for testing is good. Just make absolutely sure you don't mix up the wires and apply ground to the power side. That power comes from a module and that will burn it out in a heartbeat.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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mactube
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Jan 5, 2023, 2:08 AM
Post #16 of 20
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Mystery not solved.. lol
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I ordered a new assembly incl. led but still not working so this problem has its cause somewhere else which might not even be feasible to go after.. thanks for
all import of ideas !
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Hammer Time
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Jan 5, 2023, 5:27 AM
Post #17 of 20
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Re: Mystery not solved.. lol
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Told you it wasn't a simple problem.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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mactube
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Jan 7, 2023, 7:48 PM
Post #18 of 20
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Re: Mystery not solved.. lol
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yes yes.. that's why I'm on here .. don't need anybody to tell me .. its just the bulb or the license dealership shop to tell me they need $260 for diagnostic.
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Hammer Time
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Jan 7, 2023, 7:51 PM
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Re: Mystery not solved.. lol
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There are modules involved in this circuit so you would need some expensive equipment to diagnose it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
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Jan 7, 2023, 11:59 PM
Post #20 of 20
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Re: Mystery not solved.. lol
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? Mactube: For real and possible $260 diagnosis they better be correct and on target.
That's if they do the work most would delete that charge if done there or apply it towards total bill,
T
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