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Discussion Starter · #1 ·
So after a few months of not having it work due to a lack of a bulb and a bent bracket, my 84 firebird hasn't had an interior light since I got it. Yesterday I finally got the lightbulb and put it in only to discover that it doesn't turn off. Anyone have any ideas why this may be?
 

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1968 Convertible 400, 200 4R, 1971 Formula 400 M-22 Rock Crusher, 1984 Trans Am...........
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First thought that comes to mind is that it's hooked to the wrong fuse. One that's hot all the time rather than the proper one that shuts off. Another possibility is that the sensor that tells it to shut off is stuck at ON.
 

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']['exXxas']['itan
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I would suspect the dimmer switch for the dash lights is turned all the way up. Or a faulty switch on the hatch or doors.
 

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Here's how the dome light on a 3rd gen works. The dome light itself gets power from it's fuse. It usually runs through a splice. What makes the light turn on is that door switches and headlight switch complete the ground for the dome light.

You open a door the switch closes and ground occurs. Dome light comes on. Same with headlight switch when it is used to turn dome light on. It completes the ground and dome light comes on.

If your dome light is burning all the time, you have a short to ground somewhere in the wiring, door switches, headlight switch, or the dome light itself.
 

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Discussion Starter · #5 ·
Definitely independent of the headlight switch. I know for a fact it is connected to the CTSY fuse which also operates the horn and the cigarette lighter, which on a different note (possibly related but I have no clue) never shut off either. I'd expect that from the horn but not the cigarette lighter. Up till now I've disregarded this as a thing that was normal back then but now I'm not so sure. I know my 4runner which is only a few years newer shuts the lighter off when the key goes off.

Now as far as testing the door switches, I have no clue how to do this. I'm thinking this issue may be the reason the prong to the dome light was bent behind the housing and the courtesy light housings are no where to be seen.

Speaking of courtesy lights I went to a local junkyard the other day and got some that I hope to install and wire up once I fix this dome light problem so I'll have a full lit interior. Also picked up a gauge cluster off an '85 that goes up to 140 MPH. Didn't work on my car unfortunately. Bonus points to anyone that knows why that might be (I know the answer but I'm curious if anyone else knows)
 

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The problem with your light isn't on the power wire side of light. If it were you'd be blowing fuses. The problem lies on the ground side of the light. Something is shorted to ground and causing the ground side of light to be grounded all the time. That is why bulb is on all the time.

The door switches provide a ground for dome light when door is opened. As does the light switch when turned to dome position.

To test door switches, simply unhook the wire from the door switch. If door switch is grounded all the time causing light to burn, it will shut off when you remove the wire from it. Kick panel must be removed to get to door switch. Do both door and see if light goes off.

Unlike the camaro, the firebird has a separate light switch for the interior lights. To test it, simply remove the black wire from the switch. If there's a connector there with all wires remove connector from switch. If switch is grounded all the time, this will shut off dome light.

If removing wires from either door switch or light switch turned your dome light off, replace the offending switch.

If this did not turn dome light off. the problem is either the dome light assembly itself is grounded, or the wires that go to door switches or light switch have a short to ground.

You can test the dome light itself by simply removing the assembly from the roof. If light shuts off with assembly not touching the metal of the roof. There's the offending party. If light keeps burning with dome light hanging, your problem is with the ground wiring being shorted to ground somewhere.

Unlike a short in a power wire, a short in a ground wire doesn't hurt anything. It just keeps the light on all the time power is applied. Since dome light is powered at all times, light will stay on all the time and run your battery down.
 

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']['exXxas']['itan
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Is the hatch closing ALL the way?
 

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Discussion Starter · #8 ·
Wait the dome light has an on switch?? Where???

And I don't know why or how the the light would be wired into the hatch but yeah I'm pretty sure its closed all the way.
 

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']['exXxas']['itan
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the latch for the hatch should have a normally closed contact switch on it and when you close the hatch, it opens the switch.
 

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Discussion Starter · #10 ·
Where is the switch located? I don't recall seeing anything like that. My hatch set up is so basic I'm surprised there's any electrical things attached to it.
 

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']['exXxas']['itan
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scratch that, just looked it up. you dont have one. My 86 iroc had one.

Looking at the layout, it either has to be a door jam switch faulty, pinched wire, or the wiring for the reading lights has somehow grounded out the dome lamp since its mixed in.

http://austinthirdgen.org/mkportal/modules/contents/images/Fig16_1984_body_wiring.gif<<< try this.

Id start by unplugging your head lamp switch. if it goes out then thats the issue. If not, unplug your jam switches 1 at a time to find the faulty ground source. If you unplug them all and still on, then either reading lamp wiring has grounded the dome, or you have a pinched wire.
 

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Discussion Starter · #12 ·
Ok where do you guys see these headlamp switches?? I can't find them anywhere in the car. Here's a list of every button I have in my firebird:

Running/parking lights

headlight

gauge dimmer wheel

rear hatch heater on

rear hatch heater off

and then there's the stereo and the a/c/heater controls. There are no other buttons to my knowledge anywhere in the car. Definetely none in the housing to the domelight
 

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Just consulted a 83 firebird wiring diagram. Even though it shows the switch as being separate from headlight switch, this is just for simplicity of diagram.

The dome light on and off is built into the headlight switch. The black wire on light switch goes to ground. The white wire on light switch is coming from dome light. When you switch the dome light on, circuit is closed in light switch and dome light turns on.

Pretty much the same test for light switch as outlined above. Just make sure both white and black wires are removed from light switch. If dome light shuts off light sw is problem.

Also on the 83 wiring diagram, the power side of wiring going to dome light is white with a green stripe. This will make it easier to tell power side from ground side. Newer cars have all white wiring to dome and other courtesy lighting.
 

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Discussion Starter · #14 ·
How does the headlight switch operate the dome light? Its got two buttons one for running lights and one for the headlights. It doesn't make sense for either one to turn on the dome light
 

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The headlight switch also turns on the dome light and dims the dash lights. It pulls out for external lights, and twists (turns) for internal lighting. ....that is assuming it's the standard old-fasioned style pull switch. It's been so long since I was in a 3rd gen I can't recall. I seem to remember my '88 RS and '89 IROC having the standard pull switch though, so I assume yours does as well.

Edit: I see you list a "guage dimmer wheel", that could be it. It may go from 0-100 on brightness, but, above that "100" (or below 0) could be the dome light switch. Run it down and up and see if it "clicks". Our Ford Ranger has the dome-light on the dimmer all the way up above "full brightness", think my 4th gen is the same way.
 

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Discussion Starter · #16 ·
The firebirds have a different light setup than the camaros do. In the firebird its just a set of rocker switches and a dimmer wheel. The wheel does have a position towards the top where it clicks but I've already attempted playing with that and it made no difference.
 

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So I finally got around to pulling things apart and taking a look at all the wiring. After doing a crap done of wire tracing and what not I found out that the previous owner wired the aftermarket alarm (I HATE after market alarms partly for this reason) in a strange way that I still don't understand. So what I did was rewire the thing so now the dome light works.

Oh and I added a couple special little things

Automotive lighting Hood Automotive tire Wood Automotive design


Building Sky Window Automotive design Automotive lighting


This is a little bit of a big deal to me because as a base Firebird, mine doesn't come with those convenience lights and never had them. It comes with the housing for the lights but none of the wiring or the socket for the light bulb. I'm pretty proud of myself just because I was able to find all the things I needed and get them added all on my own without any help and without messing up.

Some pics from the process: (excuse the mess)

Automotive lighting Automotive design Automotive exterior Electricity Entertainment


Automotive parking light Automotive lighting Hood Automotive tire Bumper


Electrical wiring Gadget Computer hardware Cable Audio equipment


Flash photography Automotive lighting Tints and shades Space Wing


And finally the finished project:

Hood Automotive lighting Motor vehicle Bumper Automotive design


This is also a big deal because I haven't had light in there the whole time I've had the car and now the whole cab is illuminated. To say I'm excited is an understatement!

Edit: I have no clue why the pics are upside down but I'm too tired to fix it right now. I'll fix it tomorrow... maybe
 

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I was going to ask you how you got the car to sit on the roof to work on. But seriously, did you figure out how to turn on the dome & courtesy lights using the headlight switch. Cause all the years of 3rd gen firebird service manuals I have access to, show the headlight switch also controlling these lights.

And good job of fixing the problem.
 

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Discussion Starter · #19 ·
Thanks! And honestly, I think it would've been easier to work on this thing if it were upside down lol. A lot less back pain!

And yes I did figure out how the switch turns on the the lights. ZumpTA was right about it being the dimmer wheel. When you go up past 100 it clicks, turning on all the lights. It's really strange to me honestly but maybe I'll get used to it... or I'll just use the doors to turn them on like I did in my 4Runner lol
 
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