How to tap into interior light circuit?

[StayGold808]

Hi,

I'm wanting to tap into the door triggers for the interior dome lights. Where does the wiring from the door triggers go?

Thanks,
Adam

[boyt911sc]

Originally Posted by StayGold808

Hi,

I'm wanting to tap into the door triggers for the interior dome lights. Where does the wiring from the door triggers go?

Thanks,
Adam

Adam,

The door switches are nothing but ground contacts. Have you checked them? They have brown wires and grounded to the chassis/body. The dome lights get power directly from fuse #18. HTH.

Tony

[kidrock]

be careful pulling those door triggers, the brown ground wires are short and small. They will break easily and drop behind the jamb, and will be very difficult to fish back out.

These triggers are usually the main cause of interior light problems.

[mycastle]

Adam,

I just went through a re-wiring of my circuits for a 78 SC - my assumption is that they would be similar. Tony is correct that the passenger door and the driver door switches are simply gound connectors. The wiring is under the carpet on the passenger side, below the seat rails and runs up the passenger side behind the door frame (should have two wires, one hot, the other is ground. The ground wire comes from the interior light, down the door frame, onto the deck, and up into a hole where the ventilation/heater duct comes up out of and to the passenger side switch. The wire then goes up into the hood area, across the back of the console and then back into the cab into the door jam via the drivers side heater duct opening for the drivers side switch. It is a brown wire, but on both sides of mine there was a black protective sheath over it.

I was able to get access to the ground wires up next to the hood hinge area behind some ventilation ducting on the passenger side. It was there that the PO tied into the wire for grounding purposes for an alarm system, but it also looked like there was an original connector there to allow for ground wire splitting, maybe for that very purpose.

Again, this was for a 78 911SC and don't really know if the configuration is much different.

Regards,

Mike

[StayGold808]

Thanks for the replies...

The reason I want to tap into the door trigger, is because I want to connect it to a remote central locking system. The system has a provision to detect when a door has been opened.

So which wire should i splice into? I'm thinking it should be the ground wire from the door trigger, as the hot wire is always hot. What is the easiest way? The remote central locking control unit is located in the front trunk.

[StayGold808]

I had another go at looking for the wires...

I found a brown and red wire that was coming out of just behind the foot well blowers. It appeared to lead to the door trigger. However when i cut it the interior lights didn't go off, so had to solder it back up *sigh*...

Any more tips on finding the right wire?

[86 911 Targa]

Originally Posted by StayGold808

I had another go at looking for the wires...

I found a brown and red wire that was coming out of just behind the foot well blowers. It appeared to lead to the door trigger. However when i cut it the interior lights didn't go off, so had to solder it back up *sigh*...

Any more tips on finding the right wire?

You may have cut the speaker wire.

[StayGold808]

if i did, it was the original speaker wires, which have been upgraded...

But I don't think so, as this wire ran into the front trunk where the heater ducting goes..

[StayGold808]

In the front trunk area, behind the passenger side (for you US guys) hood hinge, Is the wire behind/near the two big round white connectors?

[nineball]

brown and red wires are the original speaker wires.

[1986911]

Here you go,

1986 Porsche 911 Alarm, Remote Starter, Keyless Entry Wiring Information
Constant 12V+ Red Ignition Switch Harness (fuse box better)
Starter Yellow Ignition Switch Harness
Ignition Red/Black Ignition Switch Harness (fuse box better)
Accessory Red/Yellow Ignition Switch Harness (fuse box better)
Tach Green Coil
Brake Switch Black/Yellow Brake Switch
Trunk Pin n/a Works with Dome Light
Parking Lights Gray/Black L And Gray/Red R at Light Switch (better spot is fuse box)
Head Lamp Yellow Fuse Panel (fuse box better spot)
Door Trigger Brown/White (-) Driver's Pin Switch
Door Lock Green/White (-) Behind right Hood hinge in Connector to Door
Door Unlock Blue/White (-)
Horn Wire Brown/White (-) Steering Column

Good luck

[StayGold808]

Thanks for the reply... I've seen the website where that info comes from before...

I just need some help locating the wire in the trunk area...

[HawgRyder]

Depending on the trigger voltage being looked for by the alarm box, you may have an easy or hard job ahead of you.
If the alarm box is looking for a falling voltage (12V - 0V) then attaching the sense wire directly to the door switch will be OK, however, I might suggest putting a blocking resistor in series to protect the alarm box (10K 1/4W would do).
This will prevent the alarm box from doing strange things with your lights.
If the box is looking for a rising voltage (0V - 12V) you may have to invert the trigger (with an inverter IC -integrated circuit ) to give you the correct trigger.
Hope this helps
Bob

[StayGold808]

The alarm has provisions for either a positive or negative door trigger input....

[StayGold808]

Originally Posted by mycastle

Adam,

I just went through a re-wiring of my circuits for a 78 SC - my assumption is that they would be similar. Tony is correct that the passenger door and the driver door switches are simply gound connectors. The wiring is under the carpet on the passenger side, below the seat rails and runs up the passenger side behind the door frame (should have two wires, one hot, the other is ground. The ground wire comes from the interior light, down the door frame, onto the deck, and up into a hole where the ventilation/heater duct comes up out of and to the passenger side switch. The wire then goes up into the hood area, across the back of the console and then back into the cab into the door jam via the drivers side heater duct opening for the drivers side switch. It is a brown wire, but on both sides of mine there was a black protective sheath over it.

I was able to get access to the ground wires up next to the hood hinge area behind some ventilation ducting on the passenger side. It was there that the PO tied into the wire for grounding purposes for an alarm system, but it also looked like there was an original connector there to allow for ground wire splitting, maybe for that very purpose.

Again, this was for a 78 911SC and don't really know if the configuration is much different.

Regards,

Mike

Mike,

Can you please give me some info on the connector so i know what to look for? I'm guessing its one of the smaller square ones...

[mycastle]

OK - little hard to see, but here is what I have.

There are two cables coming up from the interior into the hood area behind the hinge. One cable has two wires in it, the other is only a single wire.

The cable with two wires has a power and ground cable. The power goes to the interior light, the ground comes back from it. It is here where it splits out into the rectangular connector. One wire goes back down into the interior and goes to the door switch. The other wire goes all the way across and into the interior for the drivers side door.

If you are in the hood area, I seriously doubt you have speaker wires up there, they run in from under the dash area inside the cab and into the same region that the door ground wire goes, but at least in my car, they never go into the hood area.




This picture shows the rectangular plug with one in (from light) and two out (to the doors - one is light tan looking and the other is black)




A third view showing the power line that is tapped into and then goes to the light on the hood.



Hope this helps

Mike

[StayGold808]

Thanks for the reply...

I actually located the wire a couple of days ago and was meaning to post my findings for future reference..

The correct connector (at least on my car), was located behind the hood hinge on the right side of the trunk area (driver's side for US). I was looking on the passenger side and that's why i couldn't find it. There were a couple of connectors. I just disconnected them one by one with the doors open to see which one caused the interior lights to go out.

After locating the correct plug, I spliced into the Brown/White wire which is the earth side of the interior circuit.