Aux Wiring Question. (1 Viewer)

[NikP]

Okay, now we're positive it's the blue wire as the culprit. A multi-meter and some time searching should get you a solution.

 

[milesc3]

Okay, now we're positive it's the blue wire as the culprit. A multi-meter and some time searching should get you a solution.

I do have a multi-meter but I'm not 100% clear what I am looking for. I also ordered a automotive test light with voltage display.

Is the goal to find a wire that has no voltage running to it when the car ignition is on and the doors closed/dome off but does when the door is open/dome light on? It did occur to me that maybe I could tap into lights on the lighted scuff plates but perhaps I will have the same issue as with the blue wire/dome light.

@EricSarjeant indicated it could be the result of a bad relay but I'm pretty sure it's been like this since I got the truck from him. Seems to me unlikely it's the relay. Question: The there something suppose to be running to the negative terminal on the car battery? There isn't.

 

[lx200inAR]

Y

I do have a multi-meter but I'm not 100% clear what I am looking for. I also ordered a automotive test light with voltage display.

Is the goal to find a wire that has no voltage running to it when the car ignition is on and the doors closed/dome off but does when the door is open/dome light on? It did occur to me that maybe I could tap into lights on the lighted scuff plates but perhaps I will have the same issue as with the blue wire/dome light.

@EricSarjeant indicated it could be the result of a bad relay but I'm pretty sure it's been like this since I got the truck from him. Seems to me unlikely it's the relay. Question: The there something suppose to be running to the negative terminal on the car battery? There isn't.

You might read up on how relays work, just to help understand what you are trouble shooting.

The blue wire on terminal 4 goes to ground somewhere. Otherwise the relay would never work. Most instrument lighting in Toyotas is ground switched through the BCM. So the installer was attempting to piggy back into a circuit that is being switched by the BCM with the wire from terminal 4.

The first test I would do is measuring voltage at terminals 3 and 4 with truck on and off.

Set your multimeter to measure DC voltage. (Set range to cover 0-15v, use whatever setting will cover that). Put the black lead on term 4 and the red lead on term 3 and record V. Do this with ignition on and off.

This won’t fix anything but will at least give you ideas towards next steps.

 

[NikP]

Is the goal to find a wire that has no voltage running to it when the car ignition is on and the doors closed/dome off but does when the door is open/dome light on?

Theoretically yes. Although your wiring diagram suggests your looking for a grounded condition vs no voltage. To be frank, I'd advise finding someone who understands electrical circuits and how to use your multimeter.
You don't seem to understand some of the basics like what ground wires do since you're asking if something should be run to the negative side of the battery.

 

[Julian73]

term 4 is connected to the BCM under the dash by the brake pedal---presumably tapped into the dome light. See pic---that's where the blue wire runs.View attachment 3834148

View attachment 3834149

The Blue wire in this photo is the negative lead from footwell courtesy light and leads back to terminal FSPT of the Body Control Unit which should be switching the circuit to ground with one of the 4 door switches opened.
The Red/Yellow wire is the LED positive power feed from the 10A Dome Fuse with direct Battery 12V supply.

Check your voltage between Relay Term 4 (your Blue wire) and a chassis ground. Voltage should be Zero with doors closed regardless of Ign on/off

To recap: There is no issue when the ignition is off. Everything works as it should. Comes on and goes off with dome lights/door open and the override switch works. The problem is when the ignition is one the rock lights are on regardless of anything else. Door switch off/on, override switch off/on, doesn’t matter. If the ignition is on the rock lights are on.


I’ve got the dash apart with the relay accessible. I see the white and black wires coming in from the lights (each side) .


Looks like 2 blacks from lights (1 from each side) go to ground.


RELAY:

Terminal 1 top left: Two whites from lights (load) and a third from switchbank goes into top left slot 1 on the relay.

Two wires are Load wires to lights, 3rd wire is a power source bypass through the switch, bypassing the relay

Terminal 2 top right is a single red going out to I don’t know where (maybe dome)

This is your 12V power source for your ditch lights. rather than being feed direct from battery they just piggybacked form power source for the trigger circuit. Nothing wrong with this at the low averages involved.

Terminal 3 lower right is single blue (maybe from dome? Or the open door circuit signal)

per Photo this is the terminal with a number of red power leads, its correct that these should be 12V power supply.. one lead is carrying power to Term 2 and other is caring power to switch fro bypass.

Terminal 4 lower left is 3 red wires and I assume those are coming in from the power source but one is coming in from the switch in the switch bank..

Blue wire should be a triggered ground. Triggered by the doors opening. As show it should be connected to the blue negative wire of a courtesy light that feeds to the BCU and is switched to ground when a door is opened.

what's odd is a yellow wire from the switch in the switch bank is going into the headlight washer? Found that odd.

you say this lead is not connected... I don't know why they used a 2-pole switch

Any help much appreciated.

View attachment 3833215

View attachment 3833216

View attachment 3833217

 

[milesc3]

Theoretically yes. Although your wiring diagram suggests your looking for a grounded condition vs no voltage. To be frank, I'd advise finding someone who understands electrical circuits and how to use your multimeter.
You don't seem to understand some of the basics like what ground wires do since you're asking if something should be run to the negative side of the battery.

Yeah I have been reading up---I'm sure I can fix this. I'm a skilled DIYer but I haven't done a lot on the electrical circuit side but I am enjoying adding this knowledge. I know how to use the multi-meter---it's just been ass-cold here so I haven't been in a hurry to work in the garage.

Everyone in this room has been a big help and it is much appreciated.