I have been trying to find out why my door ajar light stays on all the time. I know there have been other threads, but I have read them all and non of them have fixed the problem.
I have a 1975 Stingray, everything has been working fine till this point. The passenger has one wire(white/green). The driver side has 2 wires( 1 black and one white and green) I have replaced the plungers( worked fine) so I know that it is not the plungers. However, no matter what, the light stays on. Trying for hours to find out why, but have had no luck.
Any advise would be greatly appreciated. Thanks

 

Note: The one on the hood is also in the circuit
Check it by opening the hood with the light on and press down the switch located at the center rear of the hood, some times the "L" bracket gets bent

Also the switches located in the door sills are adjustable, get a pair of pliers and pull out on the switch stem (gently) it will pull out a little, then close the door, (this is how you set the switch to the door gap)

 

Rookie question...
Do the interior lights turn off when the door is closed?
Depress both plungers manually...does Ajar light turn off?

 

The hood switch was removed by one of the previous owners,however the door ajar lights worked without it

 

Early 70's C3's had separate interior light plungers and 'Door Ajar' plungers. The DoorAjar plungers/wiring merely creates a "short" to the wiring when one of the plungers is allowed to extend. Also, there were years where some sticky-backed rubber pads were used as the contact points for the door plungers (rather than the door body panel and paint). If the rubber piece is missing, the DoorAjar light will be turned ON>
First test would be to put key into ignition and turned to Accessory position; open one door and exercise the DoorAjar plunger while watching the dash panel indicator. If it works as it should, close the door and see that the light goes out. If not, the pad could be missing.

Do this for both doors. If DoorAjar light always stays open, either there is still a problem with the hood switch/wiring or one of the door plungers is causing an electrical short ALL THE TIME, whether the plunger is depressed or not. Further investigation would require removal on the plungers (one at a time) and testing them (and associated wiring) for electrical faults.

When I say that the system presents a "short" to the wiring, it actually causes chassis ground to be connected to the lamp system.

Your '75 C3 may be different from my recollection of early 70's C3's....

 

I didn't notice at first, but my front courtesy lights were not working. I traced the wiring and found that a wire had broke. I reconnected them and now the lights work.i though that this may have been the reason why the door ajar light did not go off. Now the front and back courtesy lights go on when you open doors and they go out as they should when the door is closed. This makes me think that the door plungers are working properly. However, the door ajar light in the console never goes off. Now I am totally baffled. Any thoughts?

 

Door ajar and ccourtesy lights are different circuits. The door ajar should be at the back of the door and the courtesy lights at the front, unless they changed it in the years between

 

Did you verify which door is faulty? Like 7T1vette posted, it might be a missing rubber pad on the door causing the plunger to not get pushed in. With ignition on, if a helper pushes in the passenger side and you push in the drivers side, the light should go out.

 

When is a door not a door?

When it's ajar..

 

There is only one switch per door on the pillar. when the door is open, the door ajar and courtesy lights come on. When I close the doors, the courtesy lights will go off, but the door ajar light stays on all the time. I am assuming that if the plungers were bad that non of the lights would go off.

 

Here's a photo of a '75 that's in the for sale section, it has the door ajar switches in the location we are referring to.
Yours doesn't have these?

 

I ran into this. Look at the door. Make sure the rubber “bumper” is there. This is what the plunger meets the door. If missing your door ajar lamp won’t go out.

 

Don't have this year car, but if the circuit is a normally open, with closure to ground to activate, then a break anywhere in the circuit could keep the grounding by plunger being detected. Sounds like you already found that on the light circuit, might be another the Door Ajar path. Continuity check between both end of the circuit will tell you, if you can find both ends

 

Thank you 71 Green 454 , Being somewhat of a novice, I thought that the plungers on the pillar operated both the courtesy lights and the door ajar light. t wasn't until you posted the picture that i realized I have been looking at the wrong thing. So this morning I went to check the plungers you showed in the pictures. Left one door closed and pushed in plunger, light still remained on. Did the other side and it was the same. Again, being a novice, I would say that it is not the plungers, but an issue somewhere else. I did ground the light socket in the console to a separate ground. If i disconnect this ground, the light will go out. So now that i know what plungers operate the door ajar light, but when pushed in doesn't shut light, what should i be looking for? ANy advise is greatly appreciated.

 

Did you have a helper so you could push both plungers in a the same time? Do you have the rubber bumper attached to the doors.

With ignition on, or engine running on my '71:
In theory, if one or both doors are open, the door ajar light come on.
If both doors are closed all the way and the plungers are correctly adjusted, the door ajar light goes out.
If one or both doors are only shut only to the first click, the door ajar light comes on if plunger is correctly adjusted.
If one or both plungers are in the out position, the circuit is closed and the door ajar light comes on.
If both plungers are in the pushed in position, the circuit is open and the door ajar light goes out.

In conclusion, you need to know if the door ajar light goes out when both door plungers are pushed in. If they do, then check to see if the rubber bumpers are attached to the doors, this might be your problem as others have stated.
If the door ajar light stays on, then remove the plungers to check the wire connections.
That's all I can think of without knowing your plunger conditions....now it's time to go pour my first cup of coffee.

Rubber bumper on door, file photo: