None of them work - fuse is good. Where do I start?
Thanks

 

Are the lamps out in the center console as well?

If only the speedo and tach housing or the center bezel are out.. I would go to the printed circuit on the back of the non working unit and check the connector for the printed circuit as well as the printed circuit. On the center gauge bezel.. the top finger on the left hand side is the power for the lamps.



Here is the speedo tach pcb.. it's labeled.



You say the fuse is good... if this is the case, test for power on the left hand side of the fuse with the headlamp switch pulled in the on position. If you have power on the left side, then pull the fuse and check for corrosion in the terminals.

If you don't have power there then I would pull the headlamp switch and test there (if both are out)

I would pull the speedo tach housing.. instructions can be found here: http://willcoxcorvette.com/repairand...lp.php?hID=146.

The gray wires that power up the dash lamps originates at the headlamp switch. The power goes from he headlamp switch to the fuse panel and then to the dash lamps both speedo and tach housing as well as the center gauge cluster and heater control lamp in the top of the cluster. So it is possible your switch may be the problem.

More times than not, it's the fingers on the back of the cluster...
Then headlamp switch.
Then wiring.

If you have an issue with the wiring.. you can do a continuity test from the gray terminal on the pcb to the right hand terminal on by the fuse.

Hope this helps you

Willcox

 

More to add: no lights work at the dash or center gauge cluster, and the overhead light / foot areas lights will not go out - doors open or closed. Glove box light works as it should. Head lights and marker lights work as they should. I'm beginning to think its a bad light switch - thoughts? Just bought this car last week and finding all sort of issues to fix.

 

I'm in the same boat as you. My dash lights do not light up only the RH turn signal indicator works. My center guage lights do work. This morning I replaced the speedo tach printed circuit board. because the old one's copper lines were torn and mangled. Dash lights STILL don't work still RH turn signal indicator still works. I replaced the headlight switch in 2009 becuse the dash lights didn't work. . Been driving the car w/o dash lights since 2009. Thought replacing board would work. It didn't, may try again to find out what's wrong in another 5 years..

 

Hope replacing the switch works for you. It didn't for me.

 

Your on different circuits.. The courtesy lamps are on a different circuit than the dash lamps. If both are out.. I'd pull the headlamp switch out of the car and test the dark green wire on the switch. When you have the headlamps on, this dark green wire should be hot. The power from it is what goes to the fuse panel for the lamps.

While the courtesy lamps are not working, there are so many other things that could cause this. I would check them when you have the switch out as well. The headlamp switch doesn't power up the courtesy lamps, it grounds them. When you turn the rheostat to the left, there is a grounding leg on the front barrel of the switch that grounds out. When you do this the lamps come on.

You can see the barrel with the grounding tab in this picture in the lower right.

The courtesy lamps are the orange wire circuit... (same as the lighter, and your compartment lamp) So you telling me the glove box lamp is working tells me there is not a power sortage.. go to the sockets and see if you have power. All the courtesy lamps work by something grounding them. They are hot all the time waiting from ground. (door jamb switch, headlamp switch and so on).

 

You guys.. testing the circuit wires either at the pcb, fuse panel and other sources is the key to finding these problems. Using a tracer schematic is important to find what path different circuits take as well.

Making sure corrosion isn't present at the fuse terminals.. is very important, we see this in C3 cars more and more as they age (and leak).

Some of my trace schematics are on the website in the tech picture section or in the help and repair files.

Oldguard.. You get ready to dig into this and if I get some spare time... I'm going to help you figure this out.


Willcox

 

Here is the courtesy lamp circuit for your cars. You can see... all the orange wires are hot all the time... just waiting fro a ground. Lighter, clock and glove box are all on this same circuit.

Funny I just noticed something missing from this factory schematic.. The delay timer. I've pasted that one below the first one.

Now I have to bail on you guys.. I'm getting the stink eye from my wife... family time is here.

 

About the courtesy lights - if I understand correctly when the door closes the switch cuts the ground to make lights go out -correct? That's why the glove box light works since its on a different switch. Or do I have it backwards?

 

Hey thanks Willcox for taking the time - don't upset the little lady on my account. Remember "Happy wife, happy life".

 

While on the same circuit, the glove box operates by cutting power to the bulb with a button switch. It has a constant ground (on the switch) and just needs power.

You are correct about the courtesy lamps.. the switches make the ground when open. So you should have power at the bulb at all times.

Take care and have a great weekend. I'll check back tomorrow.

Willcox

 

I just come from outside to see if the dash lights work after replacing the pcb. The dash lights now work.
I'll be content that they work but the stock lights are "dim" The brightness was probably good for the 70s but are dim for today's standards.

 

Could one of the door switches be bad and cause the courtesy nights to stay on with the doors closed?

 

Yes it can Bludice...

 

because it can stay grounded no matter where the switch is? Learning as much as I can.....just in case.

Also, don't forget about the courtesy lamp timer.....it'll keep the lights on for a bit and if you freak out because the lights are staying on and reopen the door before the timer ends, well, you get the picture.

(that was me before I started researching the electrical circuits on the forum and my AIM for my 77...freaked out because I didn't know there was a timer)

 

Nope, the dome light stays on - thx

 

Remove both switches and inspect them.

Make sure the wires are not grounded and see if the lights stay on... it's a simple way to take the switches out of the picture.

Turbos time is a nightmare too... located behind the middle of the left dash. Yours.. if we need to go there is behind the glove box liner on the passenger side in most cases.

 

Thanks Willcox for your help, if the time delay module is removed how does the courtesy lamps react?

 

Willcox, if the time delay module is removed would the courtesy lamps stay on or not work at all?

 

If the module is removed the lamps would go out.