GKO777

On my '72, I'm trying to get my courtesy lights to work. On the fuse panel, I get 12V at the left side of the courtesy fuse, and 0V at the right side. But when I turn on the lights, I get 7V at the right side

So I suppose there is something wrong with the wiring on the headlight switch, but what could that be?

Any specific ideas, or is removing the headlight switch the first thing I should do now? If so, what is the easiest way to remove it?

Thanks!

Big2Bird

When you get a strange voltage on these fiberglass cars,95% of the time it's a bad ground somewhere. It may not seem related, but when current takes alternate current paths from where they are intended, weird things happen.
A perfect example is the tail lights. Dual filament. two sources of switch legs.The ground is between the filaments. Lose that ground, and the voltage from one filament will appear on the other filament, and up stream. The lamps will work, but not as intended.

Alan 71

Hi GKO,
Do the courtesy light works when opening the doors which uses the switches in the door jambs to illuminate them?
Regards,
Alan

GKO777

When I got the car, the switches were broken and the courtesy light fuse was removed. I just installed new switches (and a new rear compartement light), and all wiring seems fine. Before installing the 20A fuse, I measured the 2 sides of the fuse contacts and found the right side to be hot when I turn on the lights.

That's not normal, so I suppose there is some issue at the headlight swith. Because removing it on a '72 is not that easy, I was first looking for other suggestions. For instance, can I bypass the headlight switch to see if the problem is really at the switch?

derekderek

Not necessarily the headlight switch. The headlight switch doesn't have any grounds in it. It is hot in and hot out. Something some light somewhere is not grounded correctly and it is sending its 12 volts back to that courtesy light. It's a ground that's missing.

Alan 71

Hi GKO,
Might there be something in this thread that will help you?
Regards,
Alan

https://www.corvetteforum.com/forums...t-problem.html

GKO777

I don't think that's completely right: the only role of the headlight switch in the courtesy light circuit is exactly to provide a ground to that circuit when it is turned completely counter clockwise.

Pulling the headlight switch should just sent 12V to the headlights and light up the instrument panel, it should not sent anything to the courtesy light circuit...

GKO777

It's not the same issue, but the Willcox drawing helps to understand a bit:


If I understand correctly, when the headlight **** is pulled, almost all wires except the white one receive power from the orange wire. I suppose that for some reason, the power is also sent to the white wire that is involved in courtesy light circuit (and is meant as a ground wire when switch is turned counter-clockwise).

It would be great if I could somehow interrupt the white wire coming from the headlight switch to the courtesy circuit so I could verify this theory (without opening up the dash)...

henrikse

Few thoughts. If you have 12 volts on one side of a fuse you have to have 12 volts on other side or it is no good. Take the fuse out and check with an ohmeter. While you are there check both tabs on fuse as they are famous for corrosion. Ensure that your grounds are good on both door switches. These can be checked with an ohmeter or a testlight . COnnect testlight to positive battery and check the light comes on at grounds for each switch and then that with button out it is on othe side of switch. The headlamp switch should also provide ground when doors are closed and you turn all way to left.

GKO777

Henrikse, maybe I didn't express myself right, but what I meant was that I have power on both sides WITHOUT the fuse in place. this is only the case when I turn on the headlights. With headlights off, there is 0V on the right side...

henrikse

So then with headlights off and fuse in do your courtesy lights work with door open?

henrikse

Also when you turn on the headlights and get 12 volts on the right side is the headlight switch turned all the way to the left . Do the headlights, taillights and dashlights work normally?

GKO777

If I ground the white wire on the door switch, and turn on the headlights, the lights go on WITHOUT the courtesy fuse installed A bit later, the 5A fuse of the instrument panel light blows.

When the headlight switch turned completely to the right, I have 0V at the right side of the courtesy fuse. When I turn it to the left, I have a certain amount of volts according to position.

So with all this, I'm sure it is the green instrument panel light wire that somehow also powers the white wire going to the courtesy lights...

I just removed some screws to see the switch, didn't drop the column yet, so can't reach it...

henrikse

and if you don't turn on the headlights? do courtesy lights work. They are hot all the time

henrikse

Can you check on the white wire in the pic. It sounds like it has 12volts positive on it instead of ground

lvmyvt76

is this car new to you??/ Has BUBBA been working on it?? There may be some additional wiring on it some where? that Bubba has installed to rework the lights?

GKO777

So, another day and some new developments...

My main suspect was a faulty headlight switch, that would put power to the white ground wire when I turned the headlights on. So I thought that if I removed the white wire from the connector, the power would be gone from the ground circuit.

Well, not so. I removed the white wire as you can see, but when I turn on the headlights, it reads 7V again at the wire!



So to recap: turning on headlights results in about 7V in the courtesy circuit, both on the ground wire as on the right side of the courtesy fuse (with fuse removed). Learned today that the problem is not the headlight switch...

henrikse

Attached find 1073 schematic but probably same as 72. You probably have but for reference you should check your wiring in car is the same. Notice door switch on top of page 2 is where ground originates and also notice door switch at bottom of page gets ground off light switch. If you notice the orange goes all over to the clock light, 2 front courtesy lights, rear courtesy light, glove box and fuse etc. Check where this jct point is and make sure something else is not connected to it, same goes for the whiter jct points you see down by the light switch. Tracing these by hand and/or disconnecting and taking readings should help you locate.

lvmyvt76

maybe you should pull fuses until the 7 volts disappears, then see what it is causing the problem?

lionelhutz

The courtesy lights coming on with the headlights with a door switch grounded AND the instrument cluster fuse blowing TOGETHER point to there being a connection between the grey wires for the instrument cluster lights and the orange wire for the courtesy lights.

The issue can't be at the headlight switch. Sorry I read it too late to tell you this and save the time pulling it apart.

If the above schematic is true and the courtesy lights also light up the clock then I'd look at the clock since it would also have an instrument cluster light in it so it lights up while driving at night. The wires could have got crossed somewhere behind it.