both low beam and high beam headlights are out.

[jonheld]

hey thanks a ton for this JH. can i just please ask a couple more here trying to learn with apologies if i missed anything?
- the diode is preventing power from passing from the junction connector and ground toward the head relay when the stalk is turned to TAIL lights or HEAD lights?
and also it is preventing it from going "back"(?) into junction box I1 where it connects to the headlights when the dimmer ia set to HIGH or FLASH?

The diode and light retainer relay are shown on the HEADLIGHT schematic, but are not really in play here and have no function regarding troubleshooting of the headlights. They are shown because they exist.
There is a detailed schematic LIGHT AUTO TURN OFF that shows the functionality of these devices.
It's a separate circuit that allows you to leave the headlights on and they will turn off when the driver's door is opened.

- i don't quite understate the combinations witch line symbols. what is the round open circle showing me?

The combination switch is a COMBINATION of multiple closures. Each circle represents a connection point according to the switch position.
Please disregard the TAIL setting. It is shown on this schematic because it exists, but is detailed on the TAILLIGHT schematic.

With the LIGHT CONTROL SWITCH off, there is no connection.
With the LIGHT CONTROL SWITCH in the HEAD position there is a connection between pin 13 and pin 11.
This is how you interpret the diagram:

- is EA a backup ground of some kind? meaning the headlights are all grounded at EB. but also at EA? so if one is removed the headlights still work?

In earlier models there was a single ground point (EA). Toyota changed the design slightly to add an additional ground point. Since both are tied together, ground is ground no matter how you slice it.

- and rhe high beams are grounded at junction boxes E5 and E2?

They are not "junction boxes". They are splice points within the harness.
Splice points E5 and E2 are on the +12 side of the bulbs. As previously stated, all 4 bulbs receive +12 on pin 2. Pin 1 is the ground side.

 

[TreadingLight]

I recommend you set aside the diagram entirely. You're down a rabbithole of learning Toyota diagram symbols when what you need to be doing is testing your rig. 90% of the details in that diagram are irrelevant to the problem at hand.

You have one headlight out. It is probably the bulb. Step 1 is to see if you have power coming to the bulb. Get a multimeter or test light and see if you have power and ground where you should. If you don't know what to buy or how to use those tools post back here.

If you have power and ground, then go to the store and buy a bulb. Problem solved.

If you do not, then we will help you test upstream, referring to the diagram as necessary.

 

[landcruiser3DP]

The diode and light retainer relay are shown on the HEADLIGHT schematic, but are not really in play here and have no function regarding troubleshooting of the headlights. They are shown because they exist.
There is a detailed schematic LIGHT AUTO TURN OFF that shows the functionality of these devices.
It's a separate circuit that allows you to leave the headlights on and they will turn off when the driver's door is opened.

View attachment 4168537

The combination switch is a COMBINATION of multiple closures. Each circle represents a connection point according to the switch position.
Please disregard the TAIL setting. It is shown on this schematic because it exists, but is detailed on the TAILLIGHT schematic.

With the LIGHT CONTROL SWITCH off, there is no connection.
With the LIGHT CONTROL SWITCH in the HEAD position there is a connection between pin 13 and pin 11.
This is how you interpret the diagram:

View attachment 4168558

View attachment 4168616

View attachment 4168617

In earlier models there was a single ground point (EA). Toyota changed the design slightly to add an additional ground point. Since both are tied together, ground is ground no matter how you slice it.

They are not "junction boxes". They are splice points within the harness.
Splice points E5 and E2 are on the +12 side of the bulbs. As previously stated, all 4 bulbs receive +12 on pin 2. Pin 1 is the ground side.

thanks a lot JH.

i had a couple quick ones while i am studying up here please? i was able to get the headlights to work. first i tried to test the fuse box location for the LH and RH fuses.

1. i'm not sure i was sound this right so was going to confirm with you what house be doing/seeing at those locations?

then i went to test the left hand headlight harness end for power and realized is full had part of the slee harness plugged into it. so i unplugged the slew harness here and plugged the OEM harness in and of course it now works. so problem solved.

on testing the fuse box - if i turn on the headlights - i should (?) be able to put a NEG and POS probe on the little bare metal area at the rip fo each and see 12V at both these locations? and even if i remove the fuses here i shouid be able to do the same at the slots where the spade fuse slots in? like i shouid be able to see 12V here in basically in all four "locations"?

2. i am going to test the relays from the slee harness and i guess the way to do this is by applying 12V with alligator clips to the proper spades to hear if i get a click? and also i can look up the resistance i should see at these same (?) locations and i can test the resistance?

3. any idea why the slee harness wounds rip functioning or the relays would stop functioning? i assume relays in a situation like this - well they "blow" and don't simply stop working for a period of time and stay open? then start working again? also is it possible plugging in that DC refrigerator cause the problem with the slee harness? or that it may even cause a problem again? i mean i am aaauinf there is something that is preventing this from happening? is it that diode? or i guess where is a fuse for rhe cigarette outlet that should blow? or maybe i am not even thinking about this correctly...

i know that is sort of off topic but i find it really hard to have good practical examples...

 

[jonheld]

on testing the fuse box - if i turn on the headlights - i should (?) be able to put a NEG and POS probe on the little bare metal area at the rip fo each and see 12V at both these locations?

A fuse is a piece of wire. If it's intact, there's no voltage difference between the 2 sides. If the fuse is good, you'll read around 0 VDC across the fuse. If the fuse is open, you'll read around 12 VDC.

and even if i remove the fuses here i shouid be able to do the same at the slots where the spade fuse slots in?

In this case, the proper way to test for DC voltage is to have the black lead (NEG) of the meter on a good solid ground point, not across fuses or other components.
Without the fuse in place, there will be 12 volts on the "line" side terminal of the fuse (pin 1 on the schematic). The "load" side terminal of the fuse would read ground (0VDC) in this circuit (pin 2 on the schematic). Yes, there's a typo that 3 should be a 2 on the LH fuse.

2. i am going to test the relays from the slee harness and i guess the way to do this is by applying 12V with alligator clips to the proper spades to hear if i get a click?

Hearing a relay "click" is not a proper test of a relay, as the internal contacts could be faulty. You should energize the relay (click) and then check resistance across the contacts. It should read 0 ohms or very close to it.

is it possible plugging in that DC refrigerator cause the problem with the slee harness?

Well, did you tap power for the fridge off the headlight circuit???
Does the fridge only run when the headlights are on???

 

[landcruiser3DP]

A fuse is a piece of wire. If it's intact, there's no voltage difference between the 2 sides. If the fuse is good, you'll read around 0 VDC across the fuse. If the fuse is open, you'll read around 12 VDC.

In this case, the proper way to test for DC voltage is to have the black lead (NEG) of the meter on a good solid ground point, not across fuses or other components.
Without the fuse in place, there will be 12 volts on the "line" side terminal of the fuse (pin 1 on the schematic). The "load" side terminal of the fuse would read ground (0VDC) in this circuit (pin 2 on the schematic). Yes, there's a typo that 3 should be a 2 on the LH fuse.

Hearing a relay "click" is not a proper test of a relay, as the internal contacts could be faulty. You should energize the relay (click) and then check resistance across the contacts. It should read 0 ohms or very close to it.

Well, did you tap power for the fridge off the headlight circuit???
Does the fridge only run when the headlights are on???

thanks a TON for this.
please correct me here? i can go back and redo it to make sure i get it finally. testing the left hand Lo Headlight.
1. key On, with fuse out POS probe to pin 1 (line side) and NEG probe to ground i shouid see 12V.
2. key On, with fuse out POS probe to pin 2/3 (load side) and NEG probe to ground i shouid see 0V?
3. fuse in, Key On, headlights On, POS probe to POS wire at bulb connector and NEG probe to ground (or to NEG wire at bulb connector?) and is should see 12V
4. testing across a relay can be done to see if the relay is intact and i shouid see 12V.
5. does any of the above change if i disconnect the connector at the the bulb? or if the bulb is out?
6. EA and EB at the bottom are common grounds or just ground points for this circuit? i see they connect up with E4 but what is the function of the tro of them here please? they look redundant?
7. what am i calling the numbers at the fuse again? i see you said she 3 shouid be a 2 but is that because it needs to match up with the 2 at the bottom? so its like a male and female connection here?
again thanks a /ton/ for this.

 

[jonheld]

1. key On, with fuse out POS probe to pin 1 (line side) and NEG probe to ground i shouid see 12V.

Key doesn't have to be on. With the headlight switch on, yes. Remember that the headlight relay feeds the line side of both fuses. Follow the lines.

2. key On, with fuse out POS probe to pin 2/3 (load side) and NEG probe to ground i shouid see 0V?

Key position does not matter. Yes.

3. fuse in, Key On, headlights On, POS probe to POS wire at bulb connector and NEG probe to ground (or to NEG wire at bulb connector?) and is should see 12V

I would remove the bulb to test the socket. With the headlight switch on, pin 2 is hot (+12) pin 1 is ground.

4. testing across a relay can be done to see if the relay is intact and i shouid see 12V.

If you're seeing +12 at the fuse line side, then the relay has to be good. Faulty relay=no +12. Follow the lines.

5. does any of the above change if i disconnect the connector at the the bulb? or if the bulb is out?

Nope.

6. EA and EB at the bottom are common grounds or just ground points for this circuit? i see they connect up with E4 but what is the function of the tro of them here please? they look redundant?

This is all drawn out for you in the Toyota EWD.

7. what am i calling the numbers at the fuse again? i see you said she 3 shouid be a 2 but is that because it needs to match up with the 2 at the bottom? so its like a male and female connection here?
again thanks a /ton/ for this.

I'm mistaken. There is no typo. Pin 1 is common to each fuse and the load side is 2 (RH) and 3 (LH) respectively.
The "2" that you see inside the oval denotes the location of the component. In this case, the relay/fuse box on the left fender.
Again, all of this is explained in agonizing detail in the EWD.

 

[landcruiser3DP]

The diode and light retainer relay are shown on the HEADLIGHT schematic, but are not really in play here and have no function regarding troubleshooting of the headlights. They are shown because they exist.
There is a detailed schematic LIGHT AUTO TURN OFF that shows the functionality of these devices.
It's a separate circuit that allows you to leave the headlights on and they will turn off when the driver's door is opened.

View attachment 4168537

The combination switch is a COMBINATION of multiple closures. Each circle represents a connection point according to the switch position.
Please disregard the TAIL setting. It is shown on this schematic because it exists, but is detailed on the TAILLIGHT schematic.

With the LIGHT CONTROL SWITCH off, there is no connection.
With the LIGHT CONTROL SWITCH in the HEAD position there is a connection between pin 13 and pin 11.
This is how you interpret the diagram:

View attachment 4168558

View attachment 4168616

View attachment 4168617

In earlier models there was a single ground point (EA). Toyota changed the design slightly to add an additional ground point. Since both are tied together, ground is ground no matter how you slice it.

They are not "junction boxes". They are splice points within the harness.
Splice points E5 and E2 are on the +12 side of the bulbs. As previously stated, all 4 bulbs receive +12 on pin 2. Pin 1 is the ground side.

hey JH. just quickly here on the combo switch please?
OFF on the stalk is OFF on the diagram obviously.
the DASH symbol (?) on the stalk is HEAD on the stalk.
the BULB symbol on the stalk is HIGH on the diagram.
and pushing the stalk forward is FLASH on the diagram?

ao power runs to PIN 1 on the headlight relay but doesn't pass through to the R-Y wire? and power runs through tie rh combo switch on B-O (whatever that is) wire to Pin 13 and it also runs to pin 14 on the combo switch?

so if i turn headlights On ("HEAD" onthr diagram) i should see power running through W-B wire through the splice at I6, then to ground but also up to pin 9, through combo switch into pin 12 and R-Y wiring?

also the R-Y wire on the "Load Side" is also powered out of the combo switch?

and basically at some point that Headlight Relay closes and all the bulbs and Fuses are "powered" or "energized" or "live"?

anyway i think that is right (where i totally didn't see any of this before honestly) - but can you jair give me some more tips on how all this behaves? like i know i need to "close the circuit" to have anything powered (?) but like what is rhe mechanics exactly of getting that relay to close and why is it important? somehow id rhe relay doesn't close you can't have a ground (just guessing at this point...).

THANK YOU

 

[jonheld]

hey JH. just quickly here on the combo switch please?
OFF on the stalk is OFF on the diagram obviously.
the DASH symbol (?) on the stalk is HEAD on the stalk.
the BULB symbol on the stalk is HIGH on the diagram.
and pushing the stalk forward is FLASH on the diagram?

Are you honestly telling me that you don't know how your headlight switch works? C'mon now.

ao power runs to PIN 1 on the headlight relay but doesn't pass through to the R-Y wire? and power runs through tie rh combo switch on B-O (whatever that is) wire to Pin 13 and it also runs to pin 14 on the combo switch?

Both the coil (pin 3) and the line side of the headlight relay (pin 1) are getting constant +12 from the battery.
Follow the lines on the drawing.

In order to energize the relay and close the contacts, ground must be provided to pin 4 of the relay.
Ground is provided when the combination switch is in TAIL, HEAD, or FLASH.
I already drew this out for you in post #21.
Follow the lines on the drawing.

All of this stuff is very basic DC electronics dating back to the late 1800s.
You have +12 and ground to make stuff work. That's all you get and that's all you need. There's no magic here.

The most basic circuit on this vehicle is the horn.
Divide the schematic in half between the +12 side and the ground side.

The relay gets energized when the horn switch closes which completes the ground path, and the horns beep.