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Discussion Starter #1
New to the forum and going nuts with a 68 firebird vert.
Courtesy light circuit continues to short or feed back when light switch pulled on and reostat turned toward far left even with everything unplugged. There is a green wire (light switch) to right leg of fuse and grey (ground) to other leg. My question is this- Do all of the grey wires have to be grounded to correct this? Grey wires are to the dash cluster(housing grounds with screw in dash), light at heater controls(light socket grounds on metal heater control) and light at console shifter(has a black ground wire to use on the shifter). I bought an ac delco light switch just to make sure it was right. Something is going on because the previous owner did not use the circuit. They just jumped a hot wire from the light switch to power the cluster lights and the shifter light. I hate to put it all back together with correct grounds and it still pop fuses. Please ask questions and help me out! The wiring harness looks ok in the dash- not chopped up at all. Thanks Tom
 

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Re: courtesy light circuit woes

If I'm reading this right you have a few problems. As far back as I can remember
1 gray wires on GM are not grounds. gray is mostly dash light circuit.
2. Courtesy light circuit after fuse is Orange. White wire in this circuit is ground.
3. With the exception above Gm grounds are black or bare wire AFAIK.
Hope this help a little. If you have gray wire from fuse to screw on gage cluster that sounds like direct short to me. I have repaired too many aftermarket radios grounded thru the gray light wire than I care to count!

Jeff
 

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Re: courtesy light circuit woes

I agree w/ yellow69RS.

It is kind of hard to picture what you are writing. There is more than just a green wire and gray wire to the light switch. I imagine when you say fuse you mean in the fuse block. Yes, the schematics do show that. The (dark) green wire comes from the light switch. The gray is panel lighting. It sounds like both of you have that part already... So, it would make sense that the reostat part of the light switch is connected to the dark green wire. Therefore, the green wire is the "power" in the panel light circuit. The gray wire distibutes that power to the lights. The lights are grounded by other means.

In the AIM schematics, the gray wire does go to the dash instruments, stearing column, and a harness connector. The other side of the harness connector goes to either the back up switch or neutral saftey switch connector. That is all I see for gray under dash wiring. And the instrument and harness connector are the same wire, i.e. only goes between the two... The lights in the instrument cluster only need one wire, so to speak. They are then fed through the circuit board on the back of the cluster. Lights in the center console use gray wires, too.

I saved a schematic that does list most of this stuff. I think it is more of a logical diagram vs. physical one. All the instrument and a couple other dash lights (heater controls) grounds are tied together and go to the black wire that is grounded at the panel brace. All those lights are powered by gray wires. The schematic I have is just a partial of the whole thing. The light switch is cut off the scan. Or I would know what color wire does what... Heck, maybe it is just the '69 schematic from the AIM???

The courtesy light wires, as mentioned, are orange and white. They plug into the rear harness behind the left kick panel. Since they don't dim, they are on a separate circuit. The door jam switches activate them, alone w/ the light switch. There IS a orange wire to the switch. But I have never tested to see if it eventually goes to the courtesy light circuit.

If you need more rambling, let me know... lol Just kind of thinking out loud...
 

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Discussion Starter #4
Re: courtesy light circuit woes

OK- I knew there would be confusion-
1. Dash light circuit is what I am discussing- the short 5 amp fuse continues to blow if inserted when head lights turned. There was no fuse in the car when bought so someone else could not figure it out.
2. I have all harness or bulbs unhooked that contain a grey wire and still it blows.
3. So, on the fuse block you have a wires green and grey. How can it continue to blow when nothing connected on the grey side?
 

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disconnect both battery cables, and use an ohm meter to figure out which grey wire, or which circuit is shorted to chassis ground

when you figure out which wire or circuit is connecting to ground, trace the whole length of the wire ( or all wires in that circuit ) to figure out where the issue is
 

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Re: courtesy light circuit woes

OK- .
3. So, on the fuse block you have a wires green and grey. How can it continue to blow when nothing connected on the grey side?
The brief answer... the wire is grounded.

The power for the dash lights goes thru the rheostat before it goes to the fuse. that eliminates the H/L sw. The gray wire is quite probably pinched somewhere and it might not be easily seen. I once spent almost 8 hours tearing out a dash to find a wire between two pieces of metal with a bolt thru it. The next time a car came with this problem it was given to another mechanic. He didn't see it until I showed him it really didn't look pinched while it was assembled.

Jeff
 

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Discussion Starter #7
OK- will inspect gray wires closely. I did notice the rivets that hold the fuses at the fuse box were both loose on the green and gray side- That would not matter would it? Thanks
 

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Alrighty... I was doing some searches to try to figure out what all the connections on the dash switches eventually led to. From what I can tell, the green wire is actually the high beam output? And the orange is the dash light power? Did you pull the fuse block appart? Did you verify that the green and gray are actually on each side of that fuse?

Anywho, if everything is unplugged and the fuse still blows, plus one can bypass the fuse block and power the lights w/o incident, I would think that the problem is in the fuse block or wires from there to the switch. Do your light still dim via the knob when you use the jumper wire? What was the jumper wire connected to? The gray wire terminal on the switch and ???

I love mysteries, but this is getting painful... lol
 

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OK- will inspect gray wires closely. I did notice the rivets that hold the fuses at the fuse box were both loose on the green and gray side- That would not matter would it? Thanks
If this is a problem I think you'll see evidence of it being hot at some time. the problem has to be in the grauy wire somewhere to blow the little inst lp fuse, if it were elsewhere it would blow the taillamp fuse.

Jeff
 

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Alrighty... I was doing some searches to try to figure out what all the connections on the dash switches eventually led to. From what I can tell, the green wire is actually the high beam output?
Not the green wire that powers dash lights, if so the dash lights would only work with high beams on.
And the orange is the dash light power?
I believe this is courtesy lamp power at rheostat.

Do your light still dim via the knob when you use the jumper wire? What was the jumper wire connected to? The gray wire terminal on the switch and ???
Inquiring minds want to know! (me too)

Jeff
 

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Discussion Starter #13
On this question- I have jumped across the 5 amp circuit and it did blow the tail light fuse. I have a "pro" coming to take a look- stay tuned. Tom
 

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Not the green wire that powers dash lights, if so the dash lights would only work with high beams on.
Makes more sense to me! The lights get "power" from the dimmer switch. Tan for low beams, Light Green (must be where the "lime green" I was seeing in those threads came from) for high beams. That would leave the Light Blue wire on the light switch to be the "power" to the dimmer switch? The way the Tan wire is routed, it must be the "power" to the courtesy lights (and others)?


I believe this is courtesy lamp power at rheostat.
That is probably what they meant by "dash light"... Since Orange and White wires go to the courtesy lights, again, that would make sense to me... The way the Tan wire is routed, it must be the "power" to the courtesy lights (and others)?

Fun! :p
 

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Discussion Starter #15
OK problem solved-
The wiring harness to the console shifter was run BEHIND the heater box and the insulation was worn off, wires bared, and therefore a dead short. With all the boogered up wires I saw it's a wonder there were not more problems.
Whew- what a relief! Taking out the heater box, fixing the wires, and putting her back together.
 
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