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Unread 01-26-2013, 06:45 PM   #1
Quailguy
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Another wiring question

I'm trying to install a new dome light to the existing wiring that was used for the hard top light. I used a new connector and soldered all connections. Positive and negative wires are identified. When the headlight switch is turned to full left, initially the under dash light came on, but would not a second time. The new dome light did not turn on. I pulled the headlight switch and did not see a urging obvious. I then jumped the new light from the battery and that worked, so that side of things are okay. Fuses are good.
I have a less than working knowledge in using a multi-meter, but when I checked the original pos/neg wires, it showed over 12v.
I found the orange and black wires going toward the back of the fuse block, but do not know how to correctly check for power. I've read all I can find in this forum, but still stumped.
Thanks
Mike

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Unread 01-26-2013, 10:16 PM   #2
lucdog
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You do know the under dash lights are wired to have constant 12 volts positive. When you turn the headlight switch on, it completes the ground to the under dash lights. Unfortunately I don't know if the dome light is the same.
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1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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Unread 01-27-2013, 08:29 AM   #3
Quailguy
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Yes, and it lit initially, but then quit. That one may be the bulb. I think what I'm asking is how to test if this is a power problem or ground problem.
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Unread 01-27-2013, 11:15 AM   #4
Quailguy
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Okay, I'm somewhat sure it's in the ground. When
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Unread 01-27-2013, 11:22 AM   #5
Quailguy
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Lets try this again. I connected the power to the dome light and ran a jumper to a good ground. The under dash lights lit, but not the dome light. I've read in this forum there is a fuse for the circuit that runs the courtesy lights. Anyone know where I can find and check it? Also, how is the headlight switch grounded? All other lights are working correctly. If I had hair, I'd be pulling it out about now.
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Unread 01-27-2013, 11:23 AM   #6
lucdog
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Whenever I hook my test light to ground I like to test the light on a known good source. This insures the light works and there is a good ground to it. If necessary run either a wire from the battery neg. or 12v+ to where your testing. Don't forget, the Test light can be clipped to 12 + and use the prob to ground. The cigar lighter can be used for this. Just take a old Accessory plug with a length of wire stripped back, (positive and negitave) .

Bill
__________________
1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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Unread 01-27-2013, 03:33 PM   #7
lucdog
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Ok Mike, here's the harness for the under dash lights. The square connector goes to headlight switch. The round bullet connector ( 12 volts positive ) gets plugged in to the mating female connector,so you want to check that ( female bullet) with the test light, also check for ground at the switch lug when the switch is fully Counterclockwise . I believe the switch is grounded thru the dash, but not certain. There aren't any other connections for the lights.
The black wire with the tracer in this harness is positive (1976)I have another harness where this wire is blue.(1985).
Any ?'s feel free to ask.

Bill

image-851795182.jpg

Bill, and being a Firefighter is my real job, for the last 25 years.
__________________
1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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Unread 01-27-2013, 04:10 PM   #8
Matt1981CJ7
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Bill,

Thanks, my friend!! I've needed to track down the problem with my factory hardtop dome light for years.

All I know, so far, is I don't have power at the plug, near the rear of the tub, when the switch is on. The under dash light and all the dash lights work fine.

You've motivated me once again.

Matt
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Unread 01-27-2013, 06:51 PM   #9
Quailguy
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I checked the female side of the bullet connector with a test light to a ground and it lit. I'm not sure how to check the lug on the switch for ground. The square connector shows 12v+ with a multimeter. I'll take another stab tomorrow. Thanks again.
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Unread 01-28-2013, 03:23 AM   #10
John Strenk
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Quote:
Originally Posted by Quailguy View Post
I checked the female side of the bullet connector with a test light to a ground and it lit. I'm not sure how to check the lug on the switch for ground. The square connector shows 12v+ with a multimeter. I'll take another stab tomorrow. Thanks again.
That is what it should read when the terminal is not grounded. Confusing? Yes...


The contacts on the switch may be a little dirty.

Here is were the contact is made:



Here you can see the little contact the ceramic bump pushes to ground the connection.

OFF


ON



You can see the arm at the 12:00 position in the picture:



As you can see, it can get really dirty in there. Some times things get caugth in there:
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Unread 01-28-2013, 05:49 AM   #11
lucdog
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Why your meter shows 12 volts at the square connector.

12 volts positive is going thru the bullet connector, and continues thru the bulb to the square connector. That's why if you put a ground to the square connector the bulb lights. If you took the bulb out, it would now show 0 voltage at the square connector. ( the path of electricity was broken by removing the bulb.)
This is correct, right John?
Bill
__________________
1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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Unread 01-28-2013, 06:23 AM   #12
Matt1981CJ7
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Hey John,

If the dimmer switch works for the dash lights and the under dash light, but not for the dome light. Where should I begin looking?

My apologies if this is a dumb question. I've been trying to learn more about electrical issues, but my brain just doesn't absorb it like other subjects.

Sorry for the short hijack, OP.

Matt
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Unread 01-28-2013, 06:34 AM   #13
John Strenk
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Quote:
Originally Posted by lucdog View Post
Why your meter shows 12 volts at the square connector.

12 volts positive is going thru the bullet connector, and continues thru the bulb to the square connector. That's why if you put a ground to the square connector the bulb lights. If you took the bulb out, it would now show 0 voltage at the square connector. ( the path of electricity was broken by removing the bulb.)
This is correct, right John?
Bill

Right

Quote:
Originally Posted by Matt1981CJ7 View Post
Hey John,

If the dimmer switch works for the dash lights and the under dash light, but not for the dome light. Where should I begin looking?

My apologies if this is a dumb question. I've been trying to learn more about electrical issues, but my brain just doesn't absorb it like other subjects.

Sorry for the short hijack, OP.

Matt

Somehow, either the dome light is not getting power ot the grounds are not connected together.

Pull the dome light cover off and see if 12 volts is getting TO the light, then check the wiring back to ground.
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Unread 01-28-2013, 06:42 AM   #14
Matt1981CJ7
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I've checked for power at the dome light plug connector near the rear of the tub and there is none.

I'll try to trace it back to the ground.

Thanks,

Matt
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Unread 01-28-2013, 06:58 AM   #15
lucdog
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Matt, move up to the connector by the e-brake, and test there.
__________________
1957 WILLYS pickup, needs work.
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac trail Jeep.
1979 J20
1980 CJ5 trail Jeep.
1983 CJ7 pretty weekend and sometimes to work Driver in the summer, My first rebuild, if the Q-trac and 5 are broke, this one is the one to take. its just as capable as the other 2, except nice paint.
1984 Grand Wagoneer, 1 ton axles, great 360/727, and a big a$& tree fell on it .
1989 YJ the CJ to YJ conversion.
2005 TJ Rubicon.
2011 Grand Cherokee Laredo 4x4, Mrs. LUCDOG's DD.
Lots of parts not for sale, i'm a hoarder.
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