Door ajar wiring (1 Viewer)

[ATL Cruiser]

(I debated posting here or the Diesel / 24V forum. I figured this part of the wiring is the same for 12V and 24V, so I'm posting here.)

I'm on a mission to get the dome lights in my 24V HZJ77 working perfectly. Thus far, the dome lights work when opening every door EXCEPT the right rear door. The right rear is the issue.

I have tested the door ajar switch. It's a grounding switch, and it grounds great when the switch is toggled. However, there is no 24V present at the switch, meaning the problem is upstream.

So I went upstream. The switch connects to the main harness here.

The wiring schematic shows a pretty simple circuit. Just goes straight from the connector above straight to the main connector by the gas pedal.

I tested the circuit at the main connector by the gas pedal (IP1), and we have 24V at both junctions on both sides.

So, it's looking like there is a break in the main harness between the gas pedal and the right rear door. I find that hard to believe, since it's such a straight shot. However, before I start tearing the main harness apart, I'm hoping someone here has encountered this before.

 

[Felde]

As you are in and on the connectors at both ends of the line in question already..
Can't you disconnect the lie both ends and meter conductivity, using a multimeter, or by applying some voltage?
Cheers Ralf

 

[FJ73Texas]

I am interested in a solution for this because I have the same issue with my RR door operating the dome light as well (and only that one). Sometimes it works, sometimes it doesn't. Not really an issue overall because no one really rides in my cruiser except me.

I thought it was just a matter of replacing the switch but I haven't gotten around to it.

 

[ATL Cruiser]

I am interested in a solution for this because I have the same issue with my RR door operating the dome light as well (and only that one). Sometimes it works, sometimes it doesn't. Not really an issue overall because no one really rides in my cruiser except me.

I thought it was just a matter of replacing the switch but I haven't gotten around to it.

Testing the switch is incredibly easy. Just pull the cover off and remove the 10mm head bolt. It should have 12V or 24V of power there constantly. If it has power, your switch is bad. If it doesn't have power, the problem is upstream (a way harder issue to solve).

I cleaned up my other switches, and they started working. I wired brushed everything metal for the grounding and soaked the switches in alcohol.

 

[ATL Cruiser]

I bit the bullet this morning and decided to get to the bottom of the door ajar issue.

There was a break in the wire. The IP1 connector at the gas pedal showed 24V. The door switch showed 0V. Definitely a break somewhere in the wire running under the carpet along the RH floorboard. But where?

The tone generator came in handy for this. I hooked up the tone generator up to the door ajar connector and sent a tone down the length of the wire.

The tone pulsed the entire length of car until I got near the IP1 connector at the foot pedal. At that point, the tone dropped out completely. Pulling back the carpet revealed this nastiness. Someone had definitely been in here before. ... probably about 20 years ago. Lots of broken wires, corroded wires, and green crud everywhere.

I soldered and heat shrinked all the damaged wires. Right rear door ajar issue completely resolved.

 

[2fpower]

good info here @ATL Cruiser ... can I pick your brain as it seems you got this figured out....

I have 12v power going to each door switch, and the light in the cluster works for all 3 doors on my 73 series, but at my dome light it only reads 3v on the door function and no volts if you turn it on. I am thinking it is a bad ground, which i understand on a fiberglass roof.

I see only two wires going up the passenger B pillar, one is hot always, and one is hot normally, and zero volts when a doors is open.

First off, I am so confused why the door switches show 12v power. I thought this was a grounding system.... is that 12v backfeeding through a light?

Second question, should there be a third ground cable going up to the ceiling dome light? The diagram shows it grounding, but I can't pull the wires out enough to see what it is grounding to.

Thoughts?

 

[ATL Cruiser]

@2fpower I will try my best to help with this.

To confirm, the red "door ajar" dash light turns on for all three doors, correct?

But the dome light does not? Or it just turns on dimly?

The dome lamp grounds itself to the frame of the vehicle, through the screws that mount the dome lamp to the roof. That is the "third wire" you are looking for. It's actually not a wire, it is the metal of the dome lamp grounding to the frame through the metal mounting screws.

The dome lamp has three positions:
OFF: Receives 12V, and that power goes nowhere

ON: Receives 12V, and that power goes through the bulb straight to the frame. If the bulb is dim for this, it's probably because the frame, screws, or dome lamp are nasty and need to be shined up.

DOOR: Receives 12V, and that power goes to the door ajar sensors aways. The sensors will show 12V. But that 12V goes nowhere until the door is opened, and then the sensor sends that 12V to ground right there at the door.

More details here:

Guide: Rebuilding Dome Lights

The dome lights in my HZJ77 failed, and the 24V sockets were no long made. So I went ahead and rebuilt mine. This circuit is what's called a "grounding circuit" i.e. it always has power. When you flip the switch, it creates a pathway to ground, and the lights turn on. You can prove this by...

forum.ih8mud.com

 

[Felde]

The interior domelight itself should have 2 wires only: 1 positive (R or B (as per your diagram, using black for a hot wire is a bit odd, though)), one ground via the door switch (BW). Technicslly it has a direct ground (for domelight permanent switched on), too, but that is provided by the base plate of the domelight assembly. (and the screws, as @ATL Cruiser said). Hence it has no colorcode for a wire in the diagram.
The wires go to a connector located in the B pillar. (When removing the FRP top you have to disconnect that one).
12V on the door switch is normal (EDIT Corrected this), with the switch not grounding, as the bulb forwards the voltage. But it drops to Zero once grounded.
Yes, it should be a ground switching system.
If the door switch operates normal to ground it closes the circuit.
You could also remove the domelight bulb and see what that does to that 12V on the door. It should be Zero then.
You could then also measure conductivity between the domelight BW contact and the door switch, and trough door switch to ground.
Good Luck Ralf

EDIT note: I always check circuits point to point, with the consumers (bulbs etc) removed or disconnected. Hence my confusion. Sorry.

 

[2fpower]

Thank you both for the quick reply.

To confirm, the red "door ajar" dash light turns on for all three doors, correct? Yes, it works perfectly.

But the dome light does not? Or it just turns on dimly? The bulb turn on dimly, meter shows about 3v, only on the Door function. Nothing on the ON function.

I am leaning toward a bad ground on the FRP Top I will run a separate wire to where the screws are for the dome light and see if that fixes the issue. Oh, just followed your link, so I will check all those connections on the dome light... good info there.

@Felde said... You could also remove the domelight bulb and see what that does to that 12V on the door. It should be Zero then. First off, thank you for this understanding... Wouldn't I have to pull the instrument cluster bulb as well?

the reason I am digging into this was I am starting to install an alarm system, so trying to figure out what wire to connect to and if it is ground triggered or not.

Sounds like I would connect to the second wire, pin 17 on J1 as a negative triggered item.

 

[Felde]

Wouldn't I have to pull the instrument cluster bulb as well?

Mhmm. The instrument cluster is not supposed to turn lights on on door open and ignition off? Is it? In my 1985, the domelight is the only thing to be turned on by the door switch, with ignition off. But probably you are right and there are other sources in your more modern rig. I can't tell. Sorry.
And, probably you don't even have to pull the bulb, as the domelight switch also has an 'always off' position.
Cheers Ralf

 

[ATL Cruiser]

But the dome light does not? Or it just turns on dimly? The bulb turn on dimly, meter shows about 3v, only on the Door function. Nothing on the ON function.

This info helps A LOT.

Dome does not work with ON function: This means that the dome light is not able to ground itself to the frame. The 12V is going nowhere. Probably all rusty and nasty at the screw mounts. You could confirm this by running a jumper wire from the screw mount holes to a good shiny spot on the frame (the bottom two red circles in the photo below). I bet the dome light will turn on then.

Dome is dim in the DOOR position: This means that the 12V is trying to ground out at the door ajar switch, but it barely can. Probably all nasty at the door ajar switch. Try to remove the switch and clean it up. Both with alcohol inside the switch and then also clean the backside of the switch and the frame, so it's all shiny. And a fresh shiny bolt. And run a tap in those threads for good measure. I think it's 6 x 1.00mm?

You can also buy new door ajar switches suuuper cheaply, which is what I ended up doing.

 

[2fpower]

Took my door switches out and as luck would have it one is broken so you can see exactly what you’re dealing with. just a spring loaded plastic piece with a bent piece of copper that connects the two sides.... my point here is that all the contact surfaces are 1/4" back from the face of the unit, so no way to get back and clean them. Time to order new ones....