Factory headlight wiring vs. new headlight harness (1 Viewer)

[Eurasiaoverland]

I've been reading through a few of the (seemingly many) threads on replacing the sealed beam units with halogen semi-sealed beams (HSSB) taking H4/H1 bulbs.

A bit of info:

• 12V 1989 BJ60 with quad square lights.
• I want to keep the factory wiring harness as original as possible.
• I have bought:
  • 2x Koito H4 (55/60W) lights
  • 2x Toyota (Koito) H1 (55W) lights
  • The Koito twin light harness (same as the cheap Toyota upgrade pack) with 2x relays and 2x fuses
  • The additional Koito quad light harness with 1x relay and 1x fuse.

What's not clear to me is the exact nature of the weakness of the factory wiring circuit. I am doing a restoration on the harness itself and will take it conpletely apart at least as far as the firewall grommets (from the engine side) to do various repairs. I am quite prepared to upgrade the existing wiring for the headlight bulbs, but am not clear what the problem is.

I see there is only one headlight relay in the original circuit, persumably for switching both the quad main beam lights and the two dipped lights. Or is the relay only used for one circuit? With the uprgaded wiring harnesses, each circuit (3) has a relay and fuse.

Is there something fundamentally weak in the design of the factory headlight circuit itself, or can I improve it by installing thicker wires between relay and lights? Or is the weakness in the comparatively long transmission distance from the battery to the ignition / cowl harness and back to the headlights?

I'm keen to make the headlights as powerful and efficient as possible, but all those extra wires are not going to make my engine bay look very tidy. I also don't like the idea of running wiring between the lights at the front, where there is no existing harness to follow.

Any suggestions / information greatly appreciated.

EO

 

[Samppahj]

There is quite big current losses in original circuit. And it is circulated through the light switch using very thin wires. Using original wires just to control relays takes load off the light switch and properly wired from battery to relay and from relay to lights the losses becomes very small. And that equals brighter lights.

Wiring from side to side could be done behind the grill and light doors. There it will not be visible. There might be room for the relays also. I assume you don´t have that roll up screen in font of radiator so the wires could be routed there above the radiator. Also using plastic tube or nylon sleeves will tidy the wiring well. Or just wind tape around them so they will look like original wirings. And using original style connectors new wiring will blend in perfectly. In best case only visible wires will be only supply from battery to relays if you build the whole wiring loom behind grill.

 

[beatle_bayly]

There is quite big current losses in original circuit. And it is circulated through the light switch using very thin wires. Using original wires just to control relays takes load off the light switch and properly wired from battery to relay and from relay to lights the losses becomes very small. And that equals brighter lights.

Wiring from side to side could be done behind the grill and light doors. There it will not be visible. There might be room for the relays also. I assume you don´t have that roll up screen in font of radiator so the wires could be routed there above the radiator. Also using plastic tube or nylon sleeves will tidy the wiring well. Or just wind tape around them so they will look like original wirings. And using original style connectors new wiring will blend in perfectly. In best case only visible wires will be only supply from battery to relays if you build the whole wiring loom behind grill.

I agree. Use the factory wiring to control the relays.

You might also find plenty of room under the battery tray(s) to hide stuff.

From memory there is room for a cross cable underneath the radiator support frame (the part that the bonnet latch bolts to). i.e. follow the aircon pipe across the top of the condenser shown in this pic. Just ensure you protect the wires, and also the condenser and pipe from wear. That convoluted tubing used to protect wiring can rub through aluminium piping quite easily.

 

[Seth S]

The deficiency in the factory harness comes down to the wire gage and age. The wiring gage was barely adequate to support the basic bulb output when the vehicle was new. Also as these harnesses age they develop more internal resistance. Resistance in the electrical world generates heat. Wires don't like heat as it tends to damage the insulation and can result in failed wires. Also its common for the connectors on the back of the headlights to develop some corrosion...this results in a very local high resistance and this generates a lot of heat.....Ultimately this can cause the headlight connector to melt or suffer embrittlement and fall apart.

The best thing to do is to dissect your harness and build a new circuit with upgraded wires and connectors. This takes a lot of work and some tools to do correctly. So the next best thing is to use the stock harness as it is as the trigger circuit to trigger an aftermarket circuit.

 

[Eurasiaoverland]

There is quite big current losses in original circuit. And it is circulated through the light switch using very thin wires. Using original wires just to control relays takes load off the light switch and properly wired from battery to relay and from relay to lights the losses becomes very small. And that equals brighter lights.

Wiring from side to side could be done behind the grill and light doors. There it will not be visible. There might be room for the relays also. I assume you don´t have that roll up screen in font of radiator so the wires could be routed there above the radiator. Also using plastic tube or nylon sleeves will tidy the wiring well. Or just wind tape around them so they will look like original wirings. And using original style connectors new wiring will blend in perfectly. In best case only visible wires will be only supply from battery to relays if you build the whole wiring loom behind grill.

I have a headlight relay under the steering column - surely the thin wires in the headlight switch on the indicator stalk is just operating the relay, and not carrying the load of the headlight bulbs??

Given the amazing quality of your rebuild work, I am reassured by your idea of keeping it tidy. I think I can integrate parts of the three circuits in the Koito harnesses and in reality, this only needs to run between the battery terminal and the front headlights. It owuld be nice to find a base and use Toyota relays rather than the Chinese-made Omron jobs (not that I doubt they are up to the job).

I once saw one of those roll-down radiator blinds on (I think) an 80 series in Pakistan and was impressed. Have you got one? I wouldn't want one on my BJ but it would have been nice to have one on my Hilux Surf when I drove across Russia in winter!

Thanks very much for your input.

I agree. Use the factory wiring to control the relays.

You might also find plenty of room under the battery tray(s) to hide stuff.

From memory there is room for a cross cable underneath the radiator support frame (the part that the bonnet latch bolts to). i.e. follow the aircon pipe across the top of the condenser shown in this pic. Just ensure you protect the wires, and also the condenser and pipe from wear. That convoluted tubing used to protect wiring can rub through aluminium piping quite easily.View attachment 3301269

Indeed, I think I could make a fairly neat job, I have plenty of convoluted sleeving here. Interesting that the FJ62 routes the suction line across the condenser. The BJ60 has a suction hose running under the radiator shroud.

The deficiency in the factory harness comes down to the wire gage and age. The wiring gage was barely adequate to support the basic bulb output when the vehicle was new. Also as these harnesses age they develop more internal resistance. Resistance in the electrical world generates heat. Wires don't like heat as it tends to damage the insulation and can result in failed wires. Also its common for the connectors on the back of the headlights to develop some corrosion...this results in a very local high resistance and this generates a lot of heat.....Ultimately this can cause the headlight connector to melt or suffer embrittlement and fall apart.

The best thing to do is to dissect your harness and build a new circuit with upgraded wires and connectors. This takes a lot of work and some tools to do correctly. So the next best thing is to use the stock harness as it is as the trigger circuit to trigger an aftermarket circuit.

Thanks for the insight. These old non-waterproof type connectors at the front of the car are very vulnerable to corrosion. I'm toying with the idea of upgrading the harness as I have the loom apart and can easily crimp on new terminals. What's your opinion on the single headlight relay operating both circuits though? Or is one (both)? switched directly from the switch on the steering column? On my Hilux, there are separate high/dipped beam relays in the engine compartment.

EO

 

[OSS]

Using the exact same bulbs, when the system is powered through an aftermarket headlight wiring harness that uses relays, the light output from those same bulbs is significantly brighter than when they’re powered through the original wiring harness.
Reason? The small wire gauge on the original harness creates a lot of resistance = lower voltage at the bulb.

 

[Eurasiaoverland]

Using the exact same bulbs, when the system is powered through an aftermarket headlight wiring harness that uses relays, the light output from those same bulbs is significantly brighter than when they’re powered through the original wiring harness.
Reason? The small wire gauge on the original harness creates a lot of resistance = lower voltage at the bulb.

Thanks, the wire gauge factor is clear. What is not clear is the switching - is the original circuit design, with that single relay, up to driving a set of halogen lights efficiently with upgraded wires, or is it still far better to use the aftermarket harness. I have not yet sufficiently unwrapped my harness to see exactly what is switched by that relay, but as it is a four-terminal relay, I believe it could only drive one independent circuit. It would be very useful if someone knew the answer to this.

 

[NCFJ]

Toyota makes an upgrade kit for this, forget the part number. Comes with bulbs, relays, fuses and harness. Plug and play. Mount relays and fuses somewhere.

 

[Eurasiaoverland]

I just bought this from an onlier auto breaker to tidy up the Koito harnesses and have some protection for the relays. Looks like a tidy wiring job with the new Koito harnesses is the best approach.

 

[Samppahj]

I have a headlight relay under the steering column - surely the thin wires in the headlight switch on the indicator stalk is just operating the relay, and not carrying the load of the headlight bulbs??

Given the amazing quality of your rebuild work, I am reassured by your idea of keeping it tidy. I think I can integrate parts of the three circuits in the Koito harnesses and in reality, this only needs to run between the battery terminal and the front headlights. It owuld be nice to find a base and use Toyota relays rather than the Chinese-made Omron jobs (not that I doubt they are up to the job).

I once saw one of those roll-down radiator blinds on (I think) an 80 series in Pakistan and was impressed. Have you got one? I wouldn't want one on my BJ but it would have been nice to have one on my Hilux Surf when I drove across Russia in winter!

Thanks very much for your input.

EO

I might be wrong on that load going through light switch.

I have some radiator blinds. I destroyed couple of them when trying restoration on the one I have in the car. All I have are stuck and the blind itself is torn and mounting brackets missing.

And here is picture of new added wires from Power outlet box using oem connectors and electrical tape. Does blend in with others and looks oem. It is easy for you also tho have new wires blending in. The relays has to be hidden somewhere and that is probably the most difficult part. But luckily these thing are built when manufacturers did not optimize every bit of space in the engine room. And that relay box you bought can be visible and it will blend in nicely.

@Seth S is correct with corrosion building in the connector behind headlights. I had to soak mine for days with penetrating oil and still had to use such force disconnecting them that I was afraid breaking something.

 

[Seth S]

I might be wrong on that load going through light switch.

I have some radiator blinds. I destroyed couple of them when trying restoration on the one I have in the car. All I have are stuck and the blind itself is torn and mounting brackets missing.

And here is picture of new added wires from Power outlet box using oem connectors and electrical tape. Does blend in with others and looks oem. It is easy for you also tho have new wires blending in. The relays has to be hidden somewhere and that is probably the most difficult part. But luckily these thing are built when manufacturers did not optimize every bit of space in the engine room. And that relay box you bought can be visible and it will blend in nicely.

@Seth S is correct with corrosion building in the connector behind headlights. I had to soak mine for days with penetrating oil and still had to use such force disconnecting them that I was afraid breaking something.

All of the switches in a land cruiser are low current small wire circuits that trigger relays which in turn turn on and off the high current circuits which use heavier wires and components.

 

[Eurasiaoverland]

I might be wrong on that load going through light switch.

I have some radiator blinds. I destroyed couple of them when trying restoration on the one I have in the car. All I have are stuck and the blind itself is torn and mounting brackets missing.

And here is picture of new added wires from Power outlet box using oem connectors and electrical tape. Does blend in with others and looks oem. It is easy for you also tho have new wires blending in. The relays has to be hidden somewhere and that is probably the most difficult part. But luckily these thing are built when manufacturers did not optimize every bit of space in the engine room. And that relay box you bought can be visible and it will blend in nicely.

@Seth S is correct with corrosion building in the connector behind headlights. I had to soak mine for days with penetrating oil and still had to use such force disconnecting them that I was afraid breaking something.

The wiring looks very original - nice work. What are the connections - did you cut back the original headlight wires to that point? And did you ground the circuit to the body panel?

I found a picture of a twin battery BJ60 (mine is 12V single battery) which shows a battery wire running on top of the fan shroud - my shroud has the same M8 captive nuts that hold the battery wire to the fan shroud, so I can use that route to connect the two sides. I just need to find a good place to mount my relay box.

 

[Eurasiaoverland]

All of the switches in a land cruiser are low current small wire circuits that trigger relays which in turn turn on and off the high current circuits which use heavier wires and components.

Here is a part of the 1981 BJ60/HJ60 wiring diagram. It shows both a headlight and a dimmer relay:

However, in my BJ60 I am almost certain there is no dimmer relay, only a headlight relay which has two sets of terminals. I'm not good with electrics; could this seeminly single relay be used to drive all the headlight circuits (main beam in all four lights and dipped beam in the inner lights)? Surely the relay can only trigger one circuit? Or is the trigger circuit (which has noticeably thinner wires) also be one of circuits carrying current to the headlights?

 

[Seth S]

Here is a part of the 1981 BJ60/HJ60 wiring diagram. It shows both a headlight and a dimmer relay:

View attachment 3302999

However, in my BJ60 I am almost certain there is no dimmer relay, only a headlight relay which has two sets of terminals. I'm not good with electrics; could this seeminly single relay be used to drive all the headlight circuits (main beam in all four lights and dipped beam in the inner lights)? Surely the relay can only trigger one circuit? Or is the trigger circuit (which has noticeably thinner wires) also be one of circuits carrying current to the headlights?

There are headlight circuits that use a single relay for both high and low beam as you can have multiple outputs from one relay.

 

[Eurasiaoverland]

There are headlight circuits that use a single relay for both high and low beam as you can have multiple outputs from one relay.

How does a relay with four terminals (two surely being the trigger circuit) independently switch two separate circuits?

I can imagine that it might trigger one circuit, (high or dipped), but that leaves a switched headlight circuit.

Or, it could switch between circuits, but then surely (unless the headlights were always on) there would be a switch somewhere handling the high current on/off of the headlights.

 

[Samppahj]

Yes twin battery version has connection cable going over fan shroud.

4 terminal relay:

85&86 trigger and negative. 30 in. 87 out. These can be closing or opening. It switches the relay function. Opening opens the circuit when triggered and closing vice versa.

5 terminal relay:

85&86 trigger and negative. 30 in. 87a output when relay is without trigger and 87 output when relay is triggered.

Here ends my knowledge on relays

 

[Seth S]

Heres one that will blow your mind

This relay handles hi beam, low beam, high beam flash and drives a quad round lamp setup with two round lights per side, inners being high only and outers hi/lo.

 

[Samppahj]

Heres one that will blow your mind

View attachment 3303657

This relay handles hi beam, low beam, high beam flash and drives a quad round lamp setup with two round lights per side, inners being high only and outers hi/lo.

Holy s***

 

[beatle_bayly]

I'm no automotive electrician, and not sure it's relevant to this discussion, but remember the Toyotas are negatively switched. From memory there is always power on both high and low beam at the back of the light and the factory relay switches the ground.

 

[Seth S]

I'm no automotive electrician, and not sure it's relevant to this discussion, but remember the Toyotas are negatively switched. From memory there is always power on both high and low beam at the back of the light and the factory relay switches the ground.

It’s important to be aware of. It impacts LED conversions the most.