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Discussion Starter · #1 ·
Have you done it, and which wires did you use for high and low beam control going into the relay?

Thanks
Mike Golding, 72
 

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Discussion Starter · #2 ·
Mike wrote:

> Have you done it, and which wires did you
> use for high and low beam control going into
> the relay?

Well, there are several methods, depending on just what you're trying to accomplish. Like most things in life, the better methods are more work.

Let's start with a quick explanation of how the headlights are wired and go from there.

Power goes from the fuseblock directly to the common terminal on the headlights, one wire and fuse for each light. The low beam terminal from both lights are connected together and run to the dimmer switch. Same for the high beam. The common terminal of the dimmer switch goes to the headlight switch. The headlight switch grounds the lead to the dimmer switch when the headlights are turned on. In later cars, '73 for sure and some '72's, there is a passing relay connected to the high beam circuit which grounds the high beam connection between the lights and the dimmer switch. This was (I think) an attempt to keep the switch from melting.

There's a couple of problems with the stock setup and the approach to take when adding relays depends on which of the problems you're trying to cure.

Problem 1: The high current through the headlight and dimmer switch cooks the switches.

Problem 2: When using halogen conversion lights, the case of the light is GROUNDED. This shorts out the power from the fuseblock to the common terminal of the lamp. It usually doesn't short it out very well, not necessarily enough to blow the fuse, but it can eventualy melt the fuseblock. The lights also don't work very well because some of the current doesn't go through the light.

You can solve problem 1 as follows You need two relays (one for high beam, one for low). Each relay handles both lights so get at least 20 amp relays. Get normally open, or Form A relays.

Connect as follows:

Common load contact of each relay to ground. There's lots of current here so use a big fat wire and connect it to the big ground wire in the engine harness.

Cut the high beam wire between the lights and the dimmer switch where it runs by the relays. Connect the part coming from the lights to the Normally Open load contact of the high beam relay.

Connect the part coming from the dimmer switch to the negative relay coil terminal. Some relays don't care which is negative, some do. Check yours to be sure.

Connect a 12 volt source to the positive coil terminal. You have your choice here. You can use either headlight power lead, or run another fused (2 amp) lead to the battery or whatever. The problem with using a headlight power lead is that you lose BOTH your headlights if that fuse blows. You can combine the headlight power lines together with a pair of diodes if you like (that's what I used to do). Write me for part numbers and wiring procedure if you want to do that.

Do the same thing for the low beam relay.

To solve problems 1 and 2:

Now you need FOUR relays (or you have to rewire the fuseblock or run a common fuse for both headlights. On the other hand, 10 or 15 amp relays work fine 'cause each is only carrying current for one filament. Or you can use two pole relays -- then you only need two. I'll describe it as four relays because it's simpler to explain, but the other ways are probably better.

First, the coil wiring is exactly the same as for Problem 1 above. Except that you have two relays for each of high and low beam. Just connect the coils in parallel for each beam.

Cut the power wire from the fuseblock to the common terminal of the right headlight near the relays Connect the part coming from the fuse block to the common load terminal of the two right headlight relays.

Ground the part of the wire coming from the headlight. Connect it to the big black ground wire in the engine harness.

Do the same for the left headlight power wire.

Run new wires from:

Left Headlight high beam terminal to Left High Beam Relay Normally Open load contact.
Left Headlight low beam terminal to Left Low Beam Relay Normally Open load contact.
Right Headlight high beam terminal to Right High Beam Relay Normally Open load contact.
Right Headlight low beam terminal to Right Low Beam Relay Normally Open load contact.

You can, if you like, use the existing wires for one headlight or the other but you have to run new wires to the other light.

I could send a wiring diagram, either by fax, or possibly scanned in if you'd like.

I didn't mention wire colors, because I'm not sure that they're the same for all cars, but if you tell me what your wire colors are, I'll match 'em up with my wiring diagrams and tell you what is what if you like.

Good luck,

Pat

Remove the passing relay if it exists. Just unplugging it is fine.
 

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Discussion Starter · #3 ·
Mike wrote:

> Have you done it, and which wires did you
> use for high and low beam control going into
> the relay?

Well, there are several methods, depending on just what you're trying to accomplish. Like most things in life, the better methods are more work.

Let's start with a quick explanation of how the headlights are wired and go from there.

Power goes from the fuseblock directly to the common terminal on the headlights, one wire and fuse for each light. The low beam terminal from both lights are connected together and run to the dimmer switch. Same for the high beam. The common terminal of the dimmer switch goes to the headlight switch. The headlight switch grounds the lead to the dimmer switch when the headlights are turned on. In later cars, '73 for sure and some '72's, there is a passing relay connected to the high beam circuit which grounds the high beam connection between the lights and the dimmer switch. This was (I think) an attempt to keep the switch from melting.

There's a couple of problems with the stock setup and the approach to take when adding relays depends on which of the problems you're trying to cure.

Problem 1: The high current through the headlight and dimmer switch cooks the switches.

Problem 2: When using halogen conversion lights, the case of the light is GROUNDED. This shorts out the power from the fuseblock to the common terminal of the lamp. It usually doesn't short it out very well, not necessarily enough to blow the fuse, but it can eventualy melt the fuseblock. The lights also don't work very well because some of the current doesn't go through the light.

You can solve problem 1 as follows You need two relays (one for high beam, one for low). Each relay handles both lights so get at least 20 amp relays. Get normally open, or Form A relays.

Connect as follows:

Common load contact of each relay to ground. There's lots of current here so use a big fat wire and connect it to the big ground wire in the engine harness.

Cut the high beam wire between the lights and the dimmer switch where it runs by the relays. Connect the part coming from the lights to the Normally Open load contact of the high beam relay.

Connect the part coming from the dimmer switch to the negative relay coil terminal. Some relays don't care which is negative, some do. Check yours to be sure.

Connect a 12 volt source to the positive coil terminal. You have your choice here. You can use either headlight power lead, or run another fused (2 amp) lead to the battery or whatever. The problem with using a headlight power lead is that you lose BOTH your headlights if that fuse blows. You can combine the headlight power lines together with a pair of diodes if you like (that's what I used to do). Write me for part numbers and wiring procedure if you want to do that.

Do the same thing for the low beam relay.

To solve problems 1 and 2:

Now you need FOUR relays (or you have to rewire the fuseblock or run a common fuse for both headlights. On the other hand, 10 or 15 amp relays work fine 'cause each is only carrying current for one filament. Or you can use two pole relays -- then you only need two. I'll describe it as four relays because it's simpler to explain, but the other ways are probably better.

Remove the passing relay if it exists. Just unplugging it is fine.

First, the coil wiring is exactly the same as for Problem 1 above. Except that you have two relays for each of high and low beam. Just connect the coils in parallel for each beam.

Cut the power wire from the fuseblock to the common terminal of the right headlight near the relays Connect the part coming from the fuse block to the common load terminal of the two right headlight relays.

Ground the part of the wire coming from the headlight. Connect it to the big black ground wire in the engine harness.

Do the same for the left headlight power wire.

Run new wires from:

Left Headlight high beam terminal to Left High Beam Relay Normally Open load contact.
Left Headlight low beam terminal to Left Low Beam Relay Normally Open load contact.
Right Headlight high beam terminal to Right High Beam Relay Normally Open load contact.
Right Headlight low beam terminal to Right Low Beam Relay Normally Open load contact.

You can, if you like, use the existing wires for one headlight or the other but you have to run new wires to the other light.

I could send a wiring diagram, either by fax, or possibly scanned in if you'd like.

I didn't mention wire colors, because I'm not sure that they're the same for all cars, but if you tell me what your wire colors are, I'll match 'em up with my wiring diagrams and tell you what is what if you like.

Good luck,

Pat
 

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Here's a Wiring Diagram and info...

> Mike wrote:

> Well, there are several methods, depending
> on just what you're trying to accomplish.
> Like most things in life, the better methods
> are more work.

> Let's start with a quick explanation of how
> the headlights are wired and go from there.

> Power goes from the fuseblock directly to
> the common terminal on the headlights, one
> wire and fuse for each light. The low beam
> terminal from both lights are connected
> together and run to the dimmer switch. Same
> for the high beam. The common terminal of
> the dimmer switch goes to the headlight
> switch. The headlight switch grounds the
> lead to the dimmer switch when the
> headlights are turned on. In later cars, '73
> for sure and some '72's, there is a
> passing relay connected to the
> high beam circuit which grounds the high
> beam connection between the lights and the
> dimmer switch. This was (I think) an attempt
> to keep the switch from melting.

> There's a couple of problems with the stock
> setup and the approach to take when adding
> relays depends on which of the problems
> you're trying to cure.

> Problem 1: The high current through the
> headlight and dimmer switch cooks the
> switches.

> Problem 2: When using halogen conversion
> lights, the case of the light is GROUNDED.
> This shorts out the power from the fuseblock
> to the common terminal of the lamp. It
> usually doesn't short it out very well, not
> necessarily enough to blow the fuse, but it
> can eventualy melt the fuseblock. The lights
> also don't work very well because some of
> the current doesn't go through the light.

> You can solve problem 1 as follows You need
> two relays (one for high beam, one for low).
> Each relay handles both lights so get at
> least 20 amp relays. Get normally open, or
> Form A relays.

> Connect as follows:

> Common load contact of each relay to ground.
> There's lots of current here so use a big
> fat wire and connect it to the big ground
> wire in the engine harness.

> Cut the high beam wire between the lights
> and the dimmer switch where it runs by the
> relays. Connect the part coming from the
> lights to the Normally Open load contact of
> the high beam relay.

> Connect the part coming from the dimmer
> switch to the negative relay coil terminal.
> Some relays don't care which is negative,
> some do. Check yours to be sure.

> Connect a 12 volt source to the positive
> coil terminal. You have your choice here.
> You can use either headlight power lead, or
> run another fused (2 amp) lead to the
> battery or whatever. The problem with using
> a headlight power lead is that you lose BOTH
> your headlights if that fuse blows. You can
> combine the headlight power lines together
> with a pair of diodes if you like (that's
> what I used to do). Write me for part
> numbers and wiring procedure if you want to
> do that.

> Do the same thing for the low beam relay.

> To solve problems 1 and 2:

> Now you need FOUR relays (or you have to
> rewire the fuseblock or run a common fuse
> for both headlights. On the other hand, 10
> or 15 amp relays work fine 'cause each is
> only carrying current for one filament. Or
> you can use two pole relays -- then you only
> need two. I'll describe it as four relays
> because it's simpler to explain, but the
> other ways are probably better.

> Remove the passing relay if it
> exists. Just unplugging it is fine.

> First, the coil wiring is exactly the same
> as for Problem 1 above. Except that you have
> two relays for each of high and low beam.
> Just connect the coils in parallel for each
> beam.

> Cut the power wire from the fuseblock to the
> common terminal of the right headlight near
> the relays Connect the part coming from the
> fuse block to the common load terminal of
> the two right headlight relays.

> Ground the part of the wire coming from the
> headlight. Connect it to the big black
> ground wire in the engine harness.

> Do the same for the left headlight power
> wire.

> Run new wires from:

> Left Headlight high beam terminal to Left
> High Beam Relay Normally Open load contact.
> Left Headlight low beam terminal to Left Low
> Beam Relay Normally Open load contact.
> Right Headlight high beam terminal to Right
> High Beam Relay Normally Open load contact.
> Right Headlight low beam terminal to Right
> Low Beam Relay Normally Open load contact.

> You can, if you like, use the existing wires
> for one headlight or the other but you have
> to run new wires to the other light.

> I could send a wiring diagram, either by
> fax, or possibly scanned in if you'd like.

> I didn't mention wire colors, because I'm
> not sure that they're the same for all cars,
> but if you tell me what your wire colors
> are, I'll match 'em up with my wiring
> diagrams and tell you what is what if you
> like.

> Good luck,

> Pat

Check this link out...
 

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Discussion Starter · #5 ·
Re: Here's a Wiring Diagram and info...

Re:

<A HREF=http://lighting.mbz.org/tech/how_to/relays>http://lighting.mbz.org/tech/how_to/relays</A>/

It's a good article with lots of sensible advice that is applicable to the rewiring task. Three cautions about applying it directly to a 240Z.

1. The wiring diagrams show the headlight switch switching power to the lights. In the 240Z the light switch switches ground. If you wire the relays to the light switch as shown, nothing will happen when you turn the switch on.

2. The upgraded wiring diagram (with relays) shows a high beam fuse and a low beam fuse. The 240Z uses a left headlight fuse and a right headlight fuse. DO NOT use, say, the left headlight fuse for high beams and the right headlight fuse for low beams. This is DANGEROUS because one fuse will then carry 2 headlights current and the fuse (and wiring just isn't up to it).

This, by the way, is the reason I use four relays (actually, I'm planning to use solid-state high-side FET drivers instead) or two two-pole relays. I just like the idea of the stock fuses.

FWIW, I like the right/left fuse idea better the high/low because you still have a low beam light if a fuse blows. Also, each fuse carries half the current all the time rather than one carrying it all. I think Datsun got that part right and I'm sticking with it.

3. You can do it just like the wiring diagram shows, but you'll have to add new fuses (under the hood -- probably in-line fuses off the battery or alternator. And don't forget the fusible link (or a BIG UGLY FUSE) and rewire the headlight switch to supply power to the relays. It's not as simple as the article would suggest because of the backwards way the 240Z lights are wired.

Pat
 

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Pat

> Re:

> <A HREF=http://lighting.mbz.org/tech/how_to/relays>http://lighting.mbz.org/tech/how_to/relays</A>
> /

> It's a good article with lots of sensible
> advice that is applicable to the rewiring
> task. Three cautions about applying it
> directly to a 240Z.

> 1. The wiring diagrams show the headlight
> switch switching power to the lights. In the
> 240Z the light switch switches ground. If
> you wire the relays to the light switch as
> shown, nothing will happen when you turn the
> switch on.

> 2. The upgraded wiring diagram (with relays)
> shows a high beam fuse and a low beam fuse.
> The 240Z uses a left headlight fuse and a
> right headlight fuse. DO NOT use, say, the
> left headlight fuse for high beams and the
> right headlight fuse for low beams. This is
> DANGEROUS because one fuse will then carry 2
> headlights current and the fuse (and wiring
> just isn't up to it).

> This, by the way, is the reason I use four
> relays (actually, I'm planning to use
> solid-state high-side FET drivers instead)
> or two two-pole relays. I just like the idea
> of the stock fuses.

> FWIW, I like the right/left fuse idea better
> the high/low because you still have a low
> beam light if a fuse blows. Also, each fuse
> carries half the current all the time rather
> than one carrying it all. I think Datsun got
> that part right and I'm sticking with it.

> 3. You can do it just like the wiring
> diagram shows, but you'll have to add new
> fuses (under the hood -- probably in-line
> fuses off the battery or alternator. And
> don't forget the fusible link (or a BIG UGLY
> FUSE) and rewire the headlight switch to
> supply power to the relays. It's not as
> simple as the article would suggest because
> of the backwards way the 240Z lights are
> wired.

> Pat

Thanks for the info! Where is the fusible link on a 240Z?
Mike
 

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Discussion Starter · #7 ·
Re: Pat

> Thanks for the info! Where is the fusible
> link on a 240Z?
> Mike
Thats why asked the ? about it. I used that article as a guide, but knew the wiring wouldn't work for our situations. I wound up using a relay that powers on side when energized and the other when not.( this one is switched from the high beam wire, to turn on the low beams ((the nissan system is really screwy))) The deenergized on side powers a middle relay which uses headlight power to energize a third relay, which in effect, powers the high beams when the headlight switch is on and the low beams are not energized. I know its confusing, it took me a while to figure a good circuit out.
I have my headlight power coming straight off the alternator, and through 2 fuses, one for high and one for low beams. (carry a spare in case on blows).

The fusible link for the 240 comes off the wiring harness and into the starter by the battery + cable.

Mike
 

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Discussion Starter · #9 ·
Re: what are FET drivers?..

FET Drivers are sort of like solid-state relays.

The FET stands for Field Effect Transistor and is the actual circuit element that does the switching. A high-side FET driver (which is what I'm using) is a little integrated circuit that switches power (not ground) to a load and provides current limiting, thermal protection,
etc all in one neat little package.

I'm currently building a circuit board which switches power to headlights, optional driving lights, park lights, and controls turn signals and the hazard function. It gets rid of the relays, flashers, a whole bunch of wiring, and takes the high currents out of the headlight switch, dimmer switch, turn signal switch, and hazard switch. It may get combined with a replacement for the stock fuseblock too -- still working on that one. Combined with a few wiring harness upgrades, decent weatherproof connectors under the hood, and maybe a few other things, it should be pretty much bulletproof.

Yeah, I'm getting carried away, but I've lived with way too many electrical problems in my Z's for way too long and I only want to fix them one more time.

Pat
 

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Discussion Starter · #10 ·
Trons

Pat.. You are an electronics person..Your response was very interesting. Any regular guy would freak out at your description but I still understand what you are doing.. Hope all works fine..
 

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Discussion Starter · #11 ·
> Have you done it, and which wires did you
> use for high and low beam control going into
> the relay?

> Thanks
> Mike Golding, 72

I like the idea, I prefer using SCR's though for the high current loading if you don't want to use relay's which I prefer and use some latching circuit to activate them but SCR's have been made for high current apps and handle it well. I've worked on diffusion furnaces at Intel that used them running over 200A each. If you use FET's just make sure you have a good heatsink setup and keep the inputs filtered, the car's not a clean sorce for electronics and needs extra care. I'd hate to have lights glitching on and off at night. Good luck though, I am thinking of the same thing when I go to the Hella lights. You can also make it simple and get a jacob's unit. they built these things already but I'm almost sure they use relay's.
 

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Discussion Starter · #12 ·
Re: what are FET drivers?..

I like it! Cool!I think that this is a great idea. I wish I had thought it up. Oh, about the fuse box I once look at a Z-car that used the breakers from a lear jet. The only problem is that they are very expeasive. I am sure that there are some others that would be less.
 

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Discussion Starter · #13 ·
Re: what are FET drivers?..

I like it! Cool!I think that this is a great idea. I wish I had thought it up. Oh, about the fuse box I once look at a Z-car that used the breakers from a lear jet. The only problem is that they are very expensive. I am sure that there are some others that would be less.
 
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