Door trigger wire for alarm install (1992 Ford E250)

[Flyview]

Hey guys,

I'm connecting up a Viper alarm I purchased to my 1992 Ford E250 EB van. It does not have factory keyless entry or an alarm system, as far as I can tell.

I have almost found all the wires I needed with the help of this list of color coded wires I found online (link).

The last wire I need to find is for a "door trigger". I believe this could either be + (powered) or - (grounded) when any door is open. The alarm has an input for either.

I have taken off the door panel from the side door and pulled out the door switch with the wiring visible so I can test how it works and which wire I'm looking for. This is where I need your help because I don't understand how it works.

Here's what I know. There's 3 wires going up to the switch:

Black/light blue: 12v powered with door open, 12v powered with door closed.
Green/yellow: 12v powered with door open, 12v powered with door closed.
Blue/orange: 12v powered with door open, no power with door closed.

The driver's door switch has the same 3 colored wires going to it.

The wiring list I linked above says the black/light blue wire is 12V when a door is open. However, for me it's 12V whether the door is open or closed.

It would seem that I could use the blue/orange wire: it only has 12V when the door is open. The problem is this only works for that respective door. If another door is open, the wire at this door remains un-powered so it's not an indication of whether any door is open.

None of the 3 wires are ground. I checked continuity to ground and none are continuous with ground with the switch open or closed.

I don't know if all my door switches are ok. There's no dome light that comes on when a door is open. I believe the dome light is wired completely separately on the house battery circuit rather than the car battery circuit. There's no indication I can find of a door being open other than the chime going off when the driver's door is open if the key is in the ignition or the lights are left on. The chime doesn't come on if any other door is open. I don't seem to have a "door ajar" light in the instrument cluster either.

My best theory right now is the black/light blue wire should only be powered when a door is open. Maybe one of my other switches is broken and is causing this wire to be powered even with all doors closed?

So my questions are:

1) How does this switch work? What are the 3 wires? Which are supposed to be powered and when?
2) What wire can I use for a "door trigger"? Anyone have a wiring diagram for this year Econoline?

Thanks for any help!

[Bbasso]

No use able dome light, might be powered from house battery?
Dig into that, disconnect the vehicle's battery and open door. Next same for house battery.
Which didn't light the dome?

[Flyview]

Originally Posted by Bbasso

No use able dome light, might be powered from house battery?
Dig into that, disconnect the vehicle's battery and open door. Next same for house battery.
Which didn't light the dome?

Dome light isn't triggered by doors no matter which battery is connected. You can only turn it on via switches (there's 3 bulbs). It runs off of the house batteries like all the other lights.

[Flyview]

I figured it out! I was reading the manual to see how the factory dome light is supposed to work and it mentioned it'll stay on if you twist the headlamp switch. Seeing as my dome lights aren't connected like stock and they're custom and hooked up to the house batteries, my dome light doesn't turn on when a door opens OR when that switch is turned. And of course it was turned into the on position! This was affecting the door open circuit, which for this vehicle seems to be exact same as for the dome light, since that's its only real purpose.

This means I can use the black/blue wire as the positive door trigger since it gets power when any door is opened now.

It seems like one of the wires is positive when that door is opened, the other when any door is open, and the third probably always has power.