Reversible Headlight Relay Installation
03-22-21, 02:37 PM
#1
Full Member
Thread Starter
Reversible Headlight Relay Installation
I posted about this in the What Did You Do To Your FB Today? thread and was asked for details. Rather than add to the noise there, I've decided to make my own post on it.
Jump to Step 6 for the "Reversible" part
Materials List:
Relays (2)
Wire (up to you on colours, but I recommend at least 3)
Fuse(s) - I went with 1 20A for both Low and High beams
H4 pigtails (2 female, 1 male) I used Techsmart High-Temp 9003 - H4 Headlight Harness bought from Partsource/Canadian Tire and cut them up for pigtails
3/8" and 1/2" Split Loom (or not, I'm not your dad)
Electrical tape
Soldering Iron & solder (or butt connectors, your choice)
Heatshrink (I like dual wall adhesive stuff for that sealed-in wiring freshness)
Ring terminals (2)
Wire stripper/electrical crimper
Drill
Bolts
Zipties
I'm not the best with wiring, so feel free to tell me all the stuff I got wrong so I can promptly forget it and continue to do things wrong.
Step 1: The Plan
Draw up your wiring plan to save yourself headaches in the future. I was originally going to use a relay box I yanked from a junked Toyota until I learned they have their own goofy way of wiring the headlight relay, so back in the bin it goes.
This site gives a good overview to plan it out: Daniel Stern Lighting Consultancy and Supply
A model year specific wiring diagram from foxed.ca is a life saver as well.
Step 2: The PITA
Raise your headlights and disconnect your battery (might as well remove it too, makes getting to everything easier). Remove your headlight covers and cross your fingers that the screws weren't tightened down by a shaved ape like mine were. Remove 6 crews for the black surrounds and tilt them to remove, and remove/drill out 4 screws for the covers for each side.
Step 3: The Plan 2: Electric Boogaloo
Plan where to put your 2 relays, one will be high beams, one low. I put them in front of the battery. Mount them however you want, I drilled a hole in the sheet metal and used machine screws to mount them, then attempted to use steel reinforced putty to hold the nuts in place at the back. If you drill a hole paint it right away to keep the rust demons at bay, I used spray paint applied with a zip tie, but you can just soak it with a rattle can and wipe off the excess if you so choose.
Step 4: Pork Surgery
Note: a pigtail is a connector with plain wires coming out of the back (like a pig's tail).
If you got the same H4 headlight connector as I did, plug the female end into the headlight and test fit them so you can trim them to make pigtails keeping 2 things in mind:
Run and cut your wiring to size. I would go with 14 gauge if you're out buying it, but I used what I had on hand which was 12 and 10 gauge.
I would highly recommend following the OEM routing of the wiring as close as possible for your headlights and use the same plastic wiring holder thingies (I'm too lazy to look up the proper word); It worked for 40 years without pinching or breaking the wires, it should work post-relay too. I left the original wires in place until I was putting the fully connected new wires in their place so I could follow the routing as close as possible.
I run all the wiring before making any connections to make sure everything reaches, and I gave a little extra for the passenger headlight wires to make sure I wouldn't be wasting a long stretch of wire.
Use masking tape and marker to label the wires as you run them. Even if you're using different colours for everything, it can be confusing what goes where when everything is tangled together.
Plan where your fused power wire(s) will run to. I ran mine to a convenient empty slot in the fusible link box I swiped from a 2000's Suzuki (not many junked 2nd gens around here), which handled the power distribution and fusing at the same time. You can run 2 fuses, 1 for low beams and 1 for high, but I just put them on the same 20A fuse.
Step 6: The Magic Reversible Part of This Write Up
Now we use the male end pigtail of the H4 connector we carved up. Connect the black wire from the pigtail to the #86 terminal of both relays (or black wire if you have a relay harness), connect the blue wire on the pigtail to the #85 terminal (or white wire) on the Low Beam relay, and the red wire to the #85 terminal (or white wire) on the High Beam relay.
If you bought different pigtails and the colours are different, worry not! The important thing is that when you plug it into the stock H4 headlight harness, the OG Red w/ Yellow stripe wire connects to #85 on the low relay, Red w/ bLue stripe is connected to #85 on the high relay, and Black is connected to #86 on both.
Step 7: Hot Stuff
Solder/crimp your connections. A wiring harness disassembly tool is a lifesaver here for convenience sake (a small screwdriver might work too). Make sure your connections aren't where the wiring needs to bend. I recommend heat shrinking your connections to reinforce the connection and prevent corrosion.
Soldering tip: using an extra large washer and some binder clips is a convenient way to keep the wires where they need to be when you're soldering, especially when you're soldering in the engine bay.
Remember to put the heat shrink on the wire before soldering your connection.
Run your fused battery wire to terminal #30 on both relays
Run the Low Beam wire to the #87 terminal on the low relay, run the High Beam wire to the #87 terminal on the high relay.
Don't forget to run a new ground wire to the headlight pigtail and connect it with a ring terminal to a good body ground or the negative terminal.
Step 8: Wrap It All Up
With your connections all connected, and your heat shrink all shrunk, now it's time to wrap it up... in electrical tape. It's a good idea to wrap wires going to the same harness together to distribute any mechanical stress across all wires. I heavily (lots of tape, no exposed wire insulation) wrap any areas with bends, such as near the relays, near the hood hinges and under the headlight covers. Long straight runs I'll wrap sparsely (wire insulation visible between revolutions of tape) like in front of the radiator.
Next you should cover wiring in split loom. If you're frugal, focus on any areas that the wires may rub, like through the radiator shroud, around any sharp edges, etc. If you're not, just do everything, especially in front of the radiator where it's liable to get pelted by rocks and debris. Tape it wherever wiring exits the split loom to keep it from shifting, letting water in, or chafing the wire. I opted to not use split loom under the headlight covers to keep better flexibility in the wire, and instead heavily wrapped the wire in electrical tape.
Step 9: The Route of All Evil
Route your wires under the headlight cover following the factory routing as exactly as possible. Don't forget to attach your new wiring to the plastic holder/clip things (electrical tape is best, but zipties work if you can't get the clip out to wrap with tape).
Roll/fold/bunch/cram the old headlight wiring and ziptie it so it stays out of the way. Plug in your fancy male H4 relay triggering harness into the factory driver's side headlight plug. The passenger side plug is still hot, but they're built like extension cord ends, so you're unlikely to zap yourself unless you let it hang in a puddle or deliberately short it out.
Once everything's routed, ziptie any wiring that may be hanging, especially the stuff in front of the radiator, to keep it contained and minimize mechanical stress on it. Then ziptie any bunches of wires so they stay contained and out of the way.
Make sure the wiring isn't going to get rubbed or pinched by the hood hinges or the headlight motor linkages.
Step 10: Double Trouble
Double check that there's no exposed wires, everything is connected to the proper terminals, the headlight grounds are connected to a body ground or battery (oops), and nothing is going to get pinched or bent at a solder/crimped connection.
Step 11: Testing
Stick your battery back in, make sure it's not sitting on any of your new wiring, and hook it up.
Watch your wiring while someone flicks the headlight motor switch to make sure it's not bending weird or getting pinched.
Try out the headlights. Realize you forgot to connect the passenger side ground up. Connect the passenger side ground up.
Make sure both sides are about the same brightness. Try the brights, are both sides brighter? If not, you might have messed up the wiring to the headlight. You can just pull the connectors out of the harness with a harness tool or small screwdriver and swap them; the mismatched colours will be the next guy's problem.
Do they both switch brighter on high beams now? Good, now switch back and forth between low and high beams while listening to the clickety clack of the relays turn on and off (you know you want to). You're done!
Step 12: All That Stuff I Missed
I wrote this after I did the project so I probably missed some stuff in this description, feel free to correct any gaps I left. I didn't take pictures as I went because my phone's camera is dead (and I'm lazy), but you can request specific pictures and I'll use the old point and shoot camera to get them for you.
Jump to Step 6 for the "Reversible" part
Materials List:
Relays (2)
Wire (up to you on colours, but I recommend at least 3)
Fuse(s) - I went with 1 20A for both Low and High beams
H4 pigtails (2 female, 1 male) I used Techsmart High-Temp 9003 - H4 Headlight Harness bought from Partsource/Canadian Tire and cut them up for pigtails
3/8" and 1/2" Split Loom (or not, I'm not your dad)
Electrical tape
Soldering Iron & solder (or butt connectors, your choice)
Heatshrink (I like dual wall adhesive stuff for that sealed-in wiring freshness)
Ring terminals (2)
Wire stripper/electrical crimper
Drill
Bolts
Zipties
I'm not the best with wiring, so feel free to tell me all the stuff I got wrong so I can promptly forget it and continue to do things wrong.
Step 1: The Plan
Draw up your wiring plan to save yourself headaches in the future. I was originally going to use a relay box I yanked from a junked Toyota until I learned they have their own goofy way of wiring the headlight relay, so back in the bin it goes.
This site gives a good overview to plan it out: Daniel Stern Lighting Consultancy and Supply
A model year specific wiring diagram from foxed.ca is a life saver as well.
Step 2: The PITA
Raise your headlights and disconnect your battery (might as well remove it too, makes getting to everything easier). Remove your headlight covers and cross your fingers that the screws weren't tightened down by a shaved ape like mine were. Remove 6 crews for the black surrounds and tilt them to remove, and remove/drill out 4 screws for the covers for each side.
Step 3: The Plan 2: Electric Boogaloo
Plan where to put your 2 relays, one will be high beams, one low. I put them in front of the battery. Mount them however you want, I drilled a hole in the sheet metal and used machine screws to mount them, then attempted to use steel reinforced putty to hold the nuts in place at the back. If you drill a hole paint it right away to keep the rust demons at bay, I used spray paint applied with a zip tie, but you can just soak it with a rattle can and wipe off the excess if you so choose.
Step 4: Pork Surgery
Note: a pigtail is a connector with plain wires coming out of the back (like a pig's tail).
If you got the same H4 headlight connector as I did, plug the female end into the headlight and test fit them so you can trim them to make pigtails keeping 2 things in mind:
- Make sure your solders/crimped connectors will be located at a straight section of the wiring, as they will not bend.
- Make sure you keep enough wire on at least 1 of the male ends to make a pigtail for it. I used that end to make the trigger circuits for the relays.
Run and cut your wiring to size. I would go with 14 gauge if you're out buying it, but I used what I had on hand which was 12 and 10 gauge.
I would highly recommend following the OEM routing of the wiring as close as possible for your headlights and use the same plastic wiring holder thingies (I'm too lazy to look up the proper word); It worked for 40 years without pinching or breaking the wires, it should work post-relay too. I left the original wires in place until I was putting the fully connected new wires in their place so I could follow the routing as close as possible.
I run all the wiring before making any connections to make sure everything reaches, and I gave a little extra for the passenger headlight wires to make sure I wouldn't be wasting a long stretch of wire.
Use masking tape and marker to label the wires as you run them. Even if you're using different colours for everything, it can be confusing what goes where when everything is tangled together.
Plan where your fused power wire(s) will run to. I ran mine to a convenient empty slot in the fusible link box I swiped from a 2000's Suzuki (not many junked 2nd gens around here), which handled the power distribution and fusing at the same time. You can run 2 fuses, 1 for low beams and 1 for high, but I just put them on the same 20A fuse.
Step 6: The Magic Reversible Part of This Write Up
Now we use the male end pigtail of the H4 connector we carved up. Connect the black wire from the pigtail to the #86 terminal of both relays (or black wire if you have a relay harness), connect the blue wire on the pigtail to the #85 terminal (or white wire) on the Low Beam relay, and the red wire to the #85 terminal (or white wire) on the High Beam relay.
If you bought different pigtails and the colours are different, worry not! The important thing is that when you plug it into the stock H4 headlight harness, the OG Red w/ Yellow stripe wire connects to #85 on the low relay, Red w/ bLue stripe is connected to #85 on the high relay, and Black is connected to #86 on both.
Step 7: Hot Stuff
Solder/crimp your connections. A wiring harness disassembly tool is a lifesaver here for convenience sake (a small screwdriver might work too). Make sure your connections aren't where the wiring needs to bend. I recommend heat shrinking your connections to reinforce the connection and prevent corrosion.
Soldering tip: using an extra large washer and some binder clips is a convenient way to keep the wires where they need to be when you're soldering, especially when you're soldering in the engine bay.
Remember to put the heat shrink on the wire before soldering your connection.
Run your fused battery wire to terminal #30 on both relays
Run the Low Beam wire to the #87 terminal on the low relay, run the High Beam wire to the #87 terminal on the high relay.
Don't forget to run a new ground wire to the headlight pigtail and connect it with a ring terminal to a good body ground or the negative terminal.
Step 8: Wrap It All Up
With your connections all connected, and your heat shrink all shrunk, now it's time to wrap it up... in electrical tape. It's a good idea to wrap wires going to the same harness together to distribute any mechanical stress across all wires. I heavily (lots of tape, no exposed wire insulation) wrap any areas with bends, such as near the relays, near the hood hinges and under the headlight covers. Long straight runs I'll wrap sparsely (wire insulation visible between revolutions of tape) like in front of the radiator.
Next you should cover wiring in split loom. If you're frugal, focus on any areas that the wires may rub, like through the radiator shroud, around any sharp edges, etc. If you're not, just do everything, especially in front of the radiator where it's liable to get pelted by rocks and debris. Tape it wherever wiring exits the split loom to keep it from shifting, letting water in, or chafing the wire. I opted to not use split loom under the headlight covers to keep better flexibility in the wire, and instead heavily wrapped the wire in electrical tape.
Step 9: The Route of All Evil
Route your wires under the headlight cover following the factory routing as exactly as possible. Don't forget to attach your new wiring to the plastic holder/clip things (electrical tape is best, but zipties work if you can't get the clip out to wrap with tape).
Roll/fold/bunch/cram the old headlight wiring and ziptie it so it stays out of the way. Plug in your fancy male H4 relay triggering harness into the factory driver's side headlight plug. The passenger side plug is still hot, but they're built like extension cord ends, so you're unlikely to zap yourself unless you let it hang in a puddle or deliberately short it out.
Once everything's routed, ziptie any wiring that may be hanging, especially the stuff in front of the radiator, to keep it contained and minimize mechanical stress on it. Then ziptie any bunches of wires so they stay contained and out of the way.
Make sure the wiring isn't going to get rubbed or pinched by the hood hinges or the headlight motor linkages.
Step 10: Double Trouble
Double check that there's no exposed wires, everything is connected to the proper terminals, the headlight grounds are connected to a body ground or battery (oops), and nothing is going to get pinched or bent at a solder/crimped connection.
Step 11: Testing
Stick your battery back in, make sure it's not sitting on any of your new wiring, and hook it up.
Watch your wiring while someone flicks the headlight motor switch to make sure it's not bending weird or getting pinched.
Try out the headlights. Realize you forgot to connect the passenger side ground up. Connect the passenger side ground up.
Make sure both sides are about the same brightness. Try the brights, are both sides brighter? If not, you might have messed up the wiring to the headlight. You can just pull the connectors out of the harness with a harness tool or small screwdriver and swap them; the mismatched colours will be the next guy's problem.
Do they both switch brighter on high beams now? Good, now switch back and forth between low and high beams while listening to the clickety clack of the relays turn on and off (you know you want to). You're done!
Step 12: All That Stuff I Missed
I wrote this after I did the project so I probably missed some stuff in this description, feel free to correct any gaps I left. I didn't take pictures as I went because my phone's camera is dead (and I'm lazy), but you can request specific pictures and I'll use the old point and shoot camera to get them for you.
Last edited by Joekaistoe; 03-22-21 at 03:10 PM. Reason: Clarity
03-23-21, 09:39 PM
#2
OMG. What a cluster**k 
Step 13: ??
Install LED style bulbs!! Need an H-4 accepting lens like a Hella or Cibie, but these bulbs plug-and-play and if you get the correct ones, the light output is EPIC. With Zee-Ro electric load drama. If a consideration, happy to dig up the link for the set I got form SA. Transformational.
Stu A
80GS
AZ
Step 13: ??
Install LED style bulbs!! Need an H-4 accepting lens like a Hella or Cibie, but these bulbs plug-and-play and if you get the correct ones, the light output is EPIC. With Zee-Ro electric load drama. If a consideration, happy to dig up the link for the set I got form SA. Transformational.
Stu A
80GS
AZ
03-24-21, 10:46 AM
#4
Full Member
Thread Starter
I've got my eye on some JW Speaker LED headlights, but don't feel like spending the money right now.
The wiring I did looks pretty similar to the Putco harness, except I used Bosch-style relays instead of proprietary, all the wiring is cut to length so I don't have a bunch of extra to manage, and for some reason their kit doesn't have any fuses. I also had everything except the headlight harnesses in my garage already and wanted to complete the project while I had time to work on my car rather than wait half a month to have a kit shipped to me.
Someone asked for details, so I wrote it up, feel free to use whatever kit you want.
The wiring I did looks pretty similar to the Putco harness, except I used Bosch-style relays instead of proprietary, all the wiring is cut to length so I don't have a bunch of extra to manage, and for some reason their kit doesn't have any fuses. I also had everything except the headlight harnesses in my garage already and wanted to complete the project while I had time to work on my car rather than wait half a month to have a kit shipped to me.
Someone asked for details, so I wrote it up, feel free to use whatever kit you want.
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KansasCityREPU (03-24-21)
03-29-21, 04:59 PM
#5
84SE-EGI helpy-helperton
Really nice job writing this up - I especially liked the section titles. When Black Dragon (*formerly Victoria British) went under, I was glad I bought my relay harness and stored it, as it removes all of the high load electrics from the column switches, and gets a lot more volts & amps into your headlight filaments where it matters. Plus, my aged system was such that when applying the brights, ALL the front lighting would black out for about a full second... so you'd better be on a straight and not cornering.
Regardless, your wiring work is the same as the aftermarket harness replacements, though they came with the right adaptors to plug and play - making the job a lot simpler. Oh, and the positive lead on the Black Dragon harness is fusible link, that's why there's no obvious fuse holder.
gain, NICE work, and thanks for writing it all up,
Regardless, your wiring work is the same as the aftermarket harness replacements, though they came with the right adaptors to plug and play - making the job a lot simpler. Oh, and the positive lead on the Black Dragon harness is fusible link, that's why there's no obvious fuse holder.
gain, NICE work, and thanks for writing it all up,
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