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Dome light not working

 
Old 12-14-2015, 10:13 PM
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siol
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Default Dome light not working

I just replaced the dome light (figure attached)

because it was missing but it doesn't light up. Does anyone know how this light works? Is it supposed to light automatically when you open the door?
Thank you
David.
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Old 12-14-2015, 11:17 PM
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Originally Posted by siol View Post
I just replaced the dome light (figure attached)
because it was missing but it doesn't light up. Does anyone know how this light works? Is it supposed to light automatically when you open the door?
Thank you
David.
Did you check the fuse? Also a very good investment is to purchase the service manual, assembly instruction manual (AIM) and electrical drawings. You can get a copy of the electrical from one of the fourm members. https://www.corvetteforum.com/forums...or-anyone.html

Last edited by kingkohlmn; 12-14-2015 at 11:21 PM.
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Old 12-14-2015, 11:18 PM
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The dome lamp works off the door opening and off the headlamp switch grounding. The lamp is hot waiting for a ground.

You didn't say what year the car is so posting help is kind of hard. What year is the car and I'm sure more help will come.

Willcox
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Old 12-14-2015, 11:43 PM
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Default C3 79 sorry

its a C3 1979 car, sorry didn't mention it.
d.

Originally Posted by Willcox Corvette View Post
The dome lamp works off the door opening and off the headlamp switch grounding. The lamp is hot waiting for a ground.

You didn't say what year the car is so posting help is kind of hard. What year is the car and I'm sure more help will come.

Willcox
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Old 12-14-2015, 11:45 PM
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Default the fuse?

what you mean by the fuse? the light bulb is totally new. where is the fuse located in a 79 C3?
Thank you
david.


Originally Posted by kingkohlmn View Post
Did you check the fuse? Also a very good investment is to purchase the service manual, assembly instruction manual (AIM) and electrical drawings. You can get a copy of the electrical from one of the fourm members. https://www.corvetteforum.com/forums...or-anyone.html
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Old 12-15-2015, 06:23 AM
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Originally Posted by siol View Post
what you mean by the fuse? the light bulb is totally new. where is the fuse located in a 79 C3?
Thank you
david.
All it takes is 12v and a ground. The 12v is on the bulb at all times. Use a voltmeter and measure on both sides of the bulb for 12v (put the black lead on a known ground (frame, engine, negative post of battery, etc) If voltage is there you have a ground issue. When you open either door, the door switch provides a ground to the courtesy lights and the dome. Do the courtesy lights work? If so, the door switch is fine.
The most likely cause of your dome light issue is the wiring either at the dome or between there and the power or ground side. My first test would be measure for 12v, or use a test light on BOTH sides of the bulb with the lead on the test light grounded. If the voltage is missing, you have either a bad fuse, bad connection at the dome light, or a broken wire. Post back what you find and we can go from there.
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Old 12-15-2015, 06:25 AM
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You did connect both the power and the ground wires to the new dome ***'y, correct?
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Old 12-15-2015, 10:33 AM
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Default followup

the lights underneath the dashboard and glove compartment work when I open the door. this is for sure. I used one of those pens that measure current and when I put it next to the dome light nothing happens as if there is no current. What else I need to measure the 12v? Also, where is this 'fuse' located that you are mentioning?

also, I did not connect any power or ground wires to the new dome. I just got a new light for the dome and place it and that when I found out it doesnt light up. I just got the c3 a month ago and I am going through everything that doesn't work...
can you specify what ground wires I have to connect to the new dome?
Thank you a lot
david.

Originally Posted by 65GGvert View Post
All it takes is 12v and a ground. The 12v is on the bulb at all times. Use a voltmeter and measure on both sides of the bulb for 12v (put the black lead on a known ground (frame, engine, negative post of battery, etc) If voltage is there you have a ground issue. When you open either door, the door switch provides a ground to the courtesy lights and the dome. Do the courtesy lights work? If so, the door switch is fine.
The most likely cause of your dome light issue is the wiring either at the dome or between there and the power or ground side. My first test would be measure for 12v, or use a test light on BOTH sides of the bulb with the lead on the test light grounded. If the voltage is missing, you have either a bad fuse, bad connection at the dome light, or a broken wire. Post back what you find and we can go from there.

Last edited by siol; 12-15-2015 at 10:37 AM.
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Old 12-15-2015, 10:42 AM
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OK, so you only replaced the lamp. I'd take the two screws out and drop it down and see if it has two wires connected to it. They may have been disconnected.
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Old 12-15-2015, 10:46 AM
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Ok. and the fuse that you all mention? Where is it located?
d.

Originally Posted by 65GGvert View Post
OK, so you only replaced the lamp. I'd take the two screws out and drop it down and see if it has two wires connected to it. They may have been disconnected.
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Old 12-15-2015, 02:21 PM
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The fuse is in the fuse box under the dash. But the fuse isn't your problem.
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Old 12-15-2015, 03:19 PM
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Originally Posted by siol View Post
Ok. and the fuse that you all mention? Where is it located?
d.
Do you have an owner's manual? it is in section #6, lists the bulbs, fuses, etc.

The 20 amp fuse handles the clock, lighter, courtesy, anti-theft alarm, glove box, & dome. Right under the circuit breaker on the top left but as stated if those work then it is something else.

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Old 12-15-2015, 03:23 PM
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Originally Posted by siol View Post
...where is the fuse located in a 79...
Do you have a 79 owner's manual? If not, order one. When it arrives, get your FCB, sit down, and read through the manual.
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Old 12-15-2015, 05:42 PM
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Forget the fuse if your courtesy lights work. Go back to what I told you about the connections at the dome.
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Old 12-16-2015, 12:10 AM
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I just did that and both wires are connected. I checked the current using one of those pens that bip when voltage is live but nothing. So there seems to be NO current going through the wires. The problem might be somewhere else and I have no idea where to start...

Originally Posted by 65GGvert View Post
OK, so you only replaced the lamp. I'd take the two screws out and drop it down and see if it has two wires connected to it. They may have been disconnected.
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Old 12-16-2015, 06:28 AM
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Originally Posted by siol View Post
I just did that and both wires are connected. I checked the current using one of those pens that bip when voltage is live but nothing. So there seems to be NO current going through the wires. The problem might be somewhere else and I have no idea where to start...
I'm dropping out here until (unless) you measure with a voltmeter for 12v on both sides of the lamp with the negative meter lead on a KNOWN good chassis ground and report back what you get.
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Old 12-16-2015, 12:39 PM
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wow, im sorry if I offended you. I dont have the 12v, is this below what I need to measure it?
thank you

http://www.delcity.net/store/12-Volt...FQMMaQodBd0HLw

Originally Posted by 65GGvert View Post
I'm dropping out here until (unless) you measure with a voltmeter for 12v on both sides of the lamp with the negative meter lead on a KNOWN good chassis ground and report back what you get.
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Old 12-16-2015, 04:56 PM
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Originally Posted by siol View Post
wow, im sorry if I offended you. I dont have the 12v, is this below what I need to measure it?
thank you

http://www.delcity.net/store/12-Volt...FQMMaQodBd0HLw
I'm not offended, that's just the first step in troubleshooting. There should always be 12v on BOTH sides of the lamp. When you open a door, or turn the dash dimmer switch to the courtesy lights on position, each of those actions provide a ground to one end of the lamp, lighting it. If the 12v is there on both sides, you have a wiring problem, being the ground wire to the dome lamp is not connected somewhere between there and where the courtesy light wires get their ground. If the voltage is not there, you would go the other way and try to find where you lost your 12v. Post back whether you have 12v on both sides of the lamp and I can tell you a couple of things to try to narrow it down.

That meter you showed will probably work, but you can buy one for $7 at harbor freight that will read ac and dc voltage, resistance, and current. Sometimes they even have it for free with any purchase. You don't need a meter specific to car voltages. Once you fix this problem you will still have the meter to check continuity, voltages, etc.
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Old 12-17-2015, 06:28 AM
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When testing for power at the dome lamp bulb, the orange wire to your lamp is the power wire, the white wire is the ground. At no time should the white wire have 12 volts present.

The white wire ground breaks off to each of the door jamb switches and the headlamp switch and this allows the lamp bulb to receive proper ground when you open the door or turn the headlamp switch to the dome/courtesy lamp position.

Basic schematic


Delay timer schematic


Full schematic.

Last edited by Willcox Corvette; 12-17-2015 at 06:30 AM.
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Old 12-17-2015, 07:10 AM
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Originally Posted by Willcox Corvette View Post
When testing for power at the dome lamp bulb, the orange wire to your lamp is the power wire, the white wire is the ground. At no time should the white wire have 12 volts present.

The white wire ground breaks off to each of the door jamb switches and the headlamp switch and this allows the lamp bulb to receive proper ground when you open the door or turn the headlamp switch to the dome/courtesy lamp position.

Basic schematic


Delay timer schematic


Full schematic.
That's true if the ground is working. IF not and the bulb is good, 12v will be on both wires.
The white wire will also have 12v with the bulb in place when the door switch nor headlight switch is grounded. Once either switch grounds the white wire, the 12v is dropped across the bulb and the white wire will no longer read 12v. I asked him to read for 12v on both sides of the bulb (should be done with the doors closed and the courtesy lights off) just to check the bulb he put in. My bet is that he has no 12v on the orange wire to begin with, but I'm having a hard time getting that info. A "current sensor" won't read current unless the current is flowing, but the voltage will read with a voltmeter.

Last edited by 65GGvert; 12-17-2015 at 07:11 AM.
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