No interior lights when I open the drivers door on my 1971 Cutlass Convertible. I do get lights when I open the Passenger side. I assumed the door jamb switch on the drivers side was bad , so I took it out. I was surprised to see three wires--- a white, a white with a black stripe and a black. Why would there be three wires and the black would be a ground one would assume? All the door switches I see on the DIY videos are just two wire affairs, just completing a simple hot wire circuit I would think. And to make it completely confusing the old switch does in fact appear to be working. The white "hot" wire is sending juice to the black wire when the switch is closed. The white wire with the black stripe is also energized. So any wisdom on this wiring would be much appreciated. TIA.

 

The black wire is ON-OFF SW KEY-IGN-KEY-BUZZER. White w/ DBL BLACK STRIPES is DOME LAMP JAM SWITCH. WHITE wire is ground - which completes (energizes) the circuit.

 

A door jam switch is a NO (Normally Open) switch. When a door is opened, the switch becomes grounded via the WHITE WIRE. This then closes/energizes the circuit.

 

The white with black stripe is for the map/courtesy lights, the plain white is the dome light, and the black is the key minder buzzer. All three provide the negative side of these circuits which is provided by the door switch. The door switch is a spring loaded normally closed switch that is held open when the door is closed. What I would do is ground the white wire and the dome light will come on, then ground the white with black stripe and the courtesy and map lights will come on, If this happens replace the door switch. Don't worry about testing the key buzzer unless you want to.

 

Ground is the body of the switch where it's screwed into the door frame. There is no need for a "ground" wire. In all cases, the switch connects each of those wires to the body ground point when it's closed. You are reading "power" on some of the wires because you are measuring open circuit voltage. As discussed above, there are three separate circuits that are controlled by that switch, the dome lights, the courtesy lights, and the key buzzer. All of them get power from the other side of the circuit.

 

Thanks for the input. The switch I purchased was not going to work even though it is supposed to match. In the time of examining the old switch, I cleaned it up and put it back in the door recess. It sparked a little when it touched the frame. I dont understand that, but the switch must be using the ground for something. Anyway, it started working again. Just wanted some of the rust knocked off.

 

You had the door open to install the switch. Unless you disconnected the battery at the time, the dome light circuit was hot. That switch closed the circuit for the dome light, which is why is sparked when you installed it. No mystery here.

 

Someone is not paying attn to what has been posted.