Fj62 headlight stock wiring question (1 Viewer)

[mrt6644]

I'm going to do the headlight relay mod but I have a question regarding the stock wiring to the fj62 headlights.
Thy are there 3 wires that go to each of the 4 headlights?
In reg headlight mode I detected pos going to 2 of the connectors. Is the rd a ground? For some reason the continuity tester couldn't tell.
Why are there 2 positives going to the reg headlight when there are separate lights for bright?
Yes I did use the search but after 20 minutes I got tired of scrolling through irrelevant threads.

 

[Granite Grinder]

62's use the ground to activate the lights, the hi/lo is the three wire connector, the hi beam uses two wires.
The positives take care of hi/lo, though the circuit only completes through the steering column switch, which connects the ground. Makes for a funky wiring diagram, I am competent enough to make my own harness, but smart enough to just get one made and install it. Plus, if you want to run H4 lamps you need to adapt the stock wiring, H4 bulbs have a different pin configuration. I'm sure slcfj62 will chime in

 

[mrt6644]

Sorry for the repeated question, I am just a little confused.
So there are 4 headlights. 2 are dedicated brights and 2 have standard and high beams.
The outside lights have low and hi. If there is only one ground, how is the low and high switched?
I took voltage measurements when the lows were on and 2 of the 3 prongs has positive 12 volts. Why would 2 be active on low? I would think one was for low and one for high.
And the brights are activated by completing the ground circuit as well?
Sorry for the dumb question. I'm actually decent with electrical stuff but this just doesn't make sense to me right now.

62's use the ground to activate the lights, the hi/lo is the three wire connector, the hi beam uses two wires.
The positives take care of hi/lo, though the circuit only completes through the steering column switch, which connects the ground. Makes for a funky wiring diagram, I am competent enough to make my own harness, but smart enough to just get one made and install it. Plus, if you want to run H4 lamps you need to adapt the stock wiring, H4 bulbs have a different pin configuration. I'm sure slcfj62 will chime in

 

[Granite Grinder]

This is where you need someone with more skills than me, here's the best I can offer:

Looks like some funky switching going on in the switch

 

[mrt6644]

Ok, the more I look at the FJ62 stock headlight wiring, the more I want to start drinking.
I went out there with a multimeter, again, to make sense of this and it doesn't.
Ok, the outside headlights, the regular beam, have 3 blades/wires attached to it.
2 of them are hot with 12+ bolts in either low or high beam mode. And Im assuming the 3rd is just a ground that gets connected when headlights rate turned on? Why 2 pos leads? Are there 2 filaments?
So the 12v pos is applied to the 2 blades and ground is tuned on and off to activate lights?
Are these supposed to have a high beam mode? Why the 2 pos connections? Redundancy?
When I tested resistance between the so called found lead to the batt ground, the resistance was in the millions, except when off. How does that make any sense.
Were the engineers doing acid when they designed this? Or are mine messed up?
There was an alarm on this vehicle that I ripped out. I suppose its possible they tapped into the headlight circuits and altered the stock wiring?
I can't make heads or tails of the wiring diagram.
Hope someone can help.
Thanks

 

[Lead Head]

The outside bulbs have two filaments, the inners have a single.

In the outside bulbs, one filament is 55 watts, the other is 35 watts. The inside bulbs have a single 55 watt filament. Each bulb receives one +12v power feed. The outside bulbs have two separate grounds, the insides have one.

When in low beam mode, the inside lights are off, and the outside bulbs have the 55 watt filament activated. When you switch to high beams, the inside bulbs are turned on, and the outside bulbs switch to the 35 watt filament.

I believe they do this to comply with regulations regarding the maximum light output a vehicle can have.

 

[mrt6644]

So I guess that means my light wiring has been modified.
Because regardless of whether I am in Hi or Low mode, on the outside lights there are 2 wires that have +12 on them, just as in low mode.
And how can the outside lights have 2 grounds when there are only 3 conductors going to them and 2 of them are positive? Does it use the ground from the mounting screws?
I think the only answer for me is to bypass the stock wiring and use my own. I would probably have the outside lights run both filaments at the same time. I doubt it would even come close to the HID or other modern headlights in brightness.

 

[Granite Grinder]

Maybe this thread will shed some light

That was really bad

https://forum.ih8mud.com/merchandise-storefront/354712-headlight-wire-harness-fj60-fj62.html

 

[Granite Grinder]

I wouldn't wire hi/lo beam into the same circuit, I'm pretty sure you would really tick people off, or you would have to aim you headlights way down. The reflector for high beam was designed to illuminate overhead signs, when you get flashed or pulled over for driving with high beams constantly

 

[mrt6644]

Right now my outside lights have power to both + feeds to headlights, so I think thats what is happening now. I wouldn't set it up so that the bright bulbs are on at the same time.
But currently on low mode, both power feeds are active to the outside bulbs. That doesn't make any sense.
Must have been aftermarket wiring.
I only wish I had a clear understanding of how the stock wiring is supposed to work.

I wouldn't wire hi/lo beam into the same circuit, I'm pretty sure you would really tick people off, or you would have to aim you headlights way down. The reflector for high beam was designed to illuminate overhead signs, when you get flashed or pulled over for driving with high beams constantly

 

[ntsqd]

My '84 Mini is wired (& it appears so is my '84 FJ-60) where there is a relay to supply power to the headlights. Then there is a relay to ground the low beams, and another relay to ground the high beams. So Toyota works the bulbs backwards from US domestics. The common terminal on the bulb (that the US OEM's ground) is fed 12+ by the first relay. Then either the hi or the low relay grounds which ever other terminal is selected by the headlight switch. In the case of the 62's it would also ground the hi terminal on the inner pair of bulbs and the supply relay would energize one of the inner bulb pair's terminals.

Clear as mud?

 

[mrt6644]

Looks like I need to test some more. The inner lights are probably the easiest as there is one filament(I think)or at least one circuit?
But the outside lights, if I have this correct, have 2 pos leads and 2 grounds? Or are both positives the same connection? And each filament is activated by its own ground? Still doesn't explain why there is a 3 conductor connector if there are 2 separate pos and 2 separate grounds.
Oh well, I think rebuilding the transmission might be easier than this.

My '84 Mini is wired (& it appears so is my '84 FJ-60) where there is a relay to supply power to the headlights. Then there is a relay to ground the low beams, and another relay to ground the high beams. So Toyota works the bulbs backwards from US domestics. The common terminal on the bulb (that the US OEM's ground) is fed 12+ by the first relay. Then either the hi or the low relay grounds which ever other terminal is selected by the headlight switch. In the case of the 62's it would also ground the hi terminal on the inner pair of bulbs and the supply relay would energize one of the inner bulb pair's terminals.

Clear as mud?

 

[Granite Grinder]

I think ntsqd is getting close. As you can see from the schematic, positive flows to all lamps through the headlight relay. The grounds (2) connect to the dimmer switch. There are two grounds, one for the hi beams, one for the low beams. The grounds are activated through the dimmer switch, low beam is always on when you turn on the lights, the high beam circuit (which activates the hi beam on all 4 four lamps) is activated through the high beam switch. Outside lamps have 2 filaments (hi/lo) inside have 1 filament. In the higher end lamp world, for our lamps, 2 filament is referred to as an H4, single filament is H1. You can't just buy high end lamp/ lenses and install them into a 62, due to the wiring. I would suspect Toyota wired these lamps with a switched ground to keep high amperage 12v positive out of the cab. Much safer to switch ground. The other issues, even switching ground at the switch is hard on the switch and it will eventually fail. Due to having all this current being routed through the switch, there will be a power loss at the headlights, as much as 1-2v. When constructing your own harness, ideally you would use relays to power the lamps, and the headlamp switch triggers the relays, which reduces the stress on the switch significantly. Also, now that your new harness is normal, i.e. two positives, on negative you can update to better quality lenses, with a variety of different lamps albeit they will still be H4 and H1. But your H4 could be 55w low and 100w hi. Your H1 could be 120w, though DOT would have a lot to say about that. Stock lamps I believe are 35/55w (H4) and 55w (H1).
I have a new harness being fabricated by slcfj62 on this board. I posted a link to his harness above. I ordered Hella lenses and lamps from Susquehanna. The lenses are a separate item from the lamps, hence you can pick your own lamp and place it into the lens.
HTH

 

[mrt6644]

Ok, getting closer. If there are 2 positives and 2 grounds, how come there is only a 3 conductor connector?

 

[Granite Grinder]

One positive, two grounds. One ground completes the the low beam circuit, one ground completes the high beam circuit. Essentially, there are two circuits, hi/lo, they share the same positive, actually, each pair of headlamps has a separate fuse, again Toyota probably did this out of redundancy, one fuse blows you still have either left or right lamps.

 

[mrt6644]

This makes sense, you don't need 2 pos leads if the switch connects the ground.
However, then I tested the leads, 2 of the 3 had +12 volts.
This can mean one of 2 things. 1: when the circuit isn't on, it rests at positive 12 and then it switches to ground when switched on. Or 2: the stock wiring was changed by an alarm or something else.

One positive, two grounds. One ground completes the the low beam circuit, one ground completes the high beam circuit. Essentially, there are two circuits, hi/lo, they share the same positive, actually, each pair of headlamps has a separate fuse, again Toyota probably did this out of redundancy, one fuse blows you still have either left or right lamps.

 

[Granite Grinder]

That doesn't make sense, but because the switching is across ground might be better testing using ohms?? Make sure you disconnect the battery, pretty easy to blow up a meter testing voltage on the ohm setting, not that I would know anything about that

 

[mrt6644]

No it doesn't. I can't see why 2 of the 3 wires would be positive 12 when it's a switched ground configuration. And to make even less sense, I tested the supposed ground conductor to see if there was continuity to ground and there wasn't. Really bizarre.

 

[Granite Grinder]

According to the schematic, positive flows down R-W and R-L, one colour for each pair of headlamps.
These go to the switch: R-Y is the high beam circuit for all four lamps, R-G is the low beam circuit

R-W = Red with white stripe
R-L = Red with blue stripe
R-Y = Red with yellow stripe
R-G = Red with green stripe

 

[Granite Grinder]

I doubt anybody messed with the headlights, needless to say they are confusing. I think a good way to tell is checking the pin configuration on the three pin plug. What type of headlights are in the truck right now?