Wiring a headlight relay

Electrical & Ignition

  1. Biggredd2069

    Biggredd2069 Active Member

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    I tried to tag on to another post but figured I'd just post my own thread. I upgraded my headlights on my 68 Newport. They are very dim. I bought a headlight wiring harness with the new relays. The initial install looks easy and straight forward. I just don't know where to plug it in to the system. I was advised follow the headlight wires back to the firewall. I did that. Not really sure what I'm looking for to disconnect. I tried searching my FSM but not sure thats the best resource for trying to install an aftermarket part. When I follow it there is a black box full of wires along the firewall but otherwise I have no idea what I'm looking for to disconnect to connect to my relays. Anyone have a pic they can point out to me? I'll add a picture of my relays. They came with no instructions.

    20190521_215547.jpg
     
    Last edited: May 23, 2019
  2. Zymurgy

    Zymurgy Old Man with a Hat FCBO Gold Member

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    If no one gets to you with info, I did this on my 66, and can send pictures and locations. I would be able to do this until probably Friday evening.

    Great improvement, I had mine installed a couple of years ago and kept everything hidden for the most part.
     
  3. mr. fix it

    mr. fix it Old Man with a Hat

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    I've recently completed this as well.
    This is the schematic I used.

    I made my own harness up since I have experience in automotive wiring and have the wiring on hand.

    I had to buy new headlight sockets so I could avoid splicing the thinner wires to the heavier gauge I chose to use

    also have a test light to double check which wire is which for the high & low beam feeds

    e94b038ea9622b59c238a9ae41c80442.jpg
     
    Last edited: May 23, 2019
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  4. mr. fix it

    mr. fix it Old Man with a Hat

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    Here's a good relay wiring schematic for the actual relay itself.
    upload_2019-5-23_13-34-5.png
     
    Last edited: May 23, 2019
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  5. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    Most of the time, dim headlights are not caused by a faulty harness. Check the fire wall plug for corrosion and clean as necessary. There is a ground wire for the headlights, usually on the core support, check ground connection mount for corrosion. For reasons unknown, a lot of these grounds were mounted next to the battery and got corroded from battery acid. Take a volt meter and see what voltage you are getting to the headlights, it should be the same as battery voltage with the vehicle running. If the voltage is lower than battery voltage, you may have a corroded light switch (bad contacts). Check all of these things before messing with the stock harness. The above considerations should be checked even if you are going to install a relay setup as relays will not cure the corrosion issues causing the dim lights, especially if the ground is bad.

    Dave
     
    Last edited: May 23, 2019
  6. mr. fix it

    mr. fix it Old Man with a Hat

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    I agree with you Dave to a certain degree.
    All good points to consider:thumbsup:
    It's always a good thing to review/clean/replace any corroded terminals/connectors in the old circuit.
    The main advantage of adding the relays is to off load the load on the aging electrical circuit including the dimmer switch & headlight switch as well
     
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  7. Biggredd2069

    Biggredd2069 Active Member

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    I will definitely check for corrosion and wear as I do want it working proper. I do have a tester and will go through the motions. I've read this is a good upgrade regardless. But I still don't see where specifically you guys are splicing this in within the engine bay. I understand the idea of how to wire it up, I'm just confused where you are splicing in. The connections on my harness lead me to believe I'm just unhooking something and plugging it on there. Am I cutting a wire? or just unplugging/unscrewing something?
     
  8. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    These aftermarket harnesses come in a lot of different styles and few are a plug and play item.. There is usually not another connection between the firewall plug and the headlights. You will probably have to splice into the existing harness.

    Dave
     
  9. luigi164

    luigi164 Active Member

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  10. jct

    jct Senior Member FCBO Gold Member

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    Plug and play is the way to go
     
  11. Biggredd2069

    Biggredd2069 Active Member

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    JCT, if its plug and play where are you unplugging?

    The daniel stern article is good. I have a good idea how all of it works and is wired. Just want to know where to unplug or cut.
     
  12. mr. fix it

    mr. fix it Old Man with a Hat

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    The headlight sockets from the headlights...
     
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  13. mr. fix it

    mr. fix it Old Man with a Hat

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    If you have the full P&P kit then you will unplug the headlight sockets and put the kit in between.
    Even those kits need a relay 12v power source.
    Since I have never purchased one I can't say for sure if this is the case.
     
  14. mr. fix it

    mr. fix it Old Man with a Hat

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    Can you post more pictures of what you bought? this can help clarify a lot of things for you & us trying to help with suggestions.
     
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  15. LocuMob

    LocuMob Fluid Technician with a hat FCBO Gold Member

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    Crackedback over on FABO sells two and four headlight wiring/relay kits, they are supposed to be plug and play.
     
  16. Biggredd2069

    Biggredd2069 Active Member

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    I'll have to post pics tomorrow. I won't be home til midnight. The kit is a 4 headlight kit. The headlight plugs are obvious plug and play. The positive and negative are obvious. Its the first picture I mentioned that is the confusing part. I don't know where to plug that in. The rest is straight forward.
     
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  17. 67Monaco

    67Monaco Old Man with a Hat

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    I fused low and high seperately this way if one fuse pops id still have another avenue to get me home.
     
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  18. LocuMob

    LocuMob Fluid Technician with a hat FCBO Gold Member

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    Aren't those just the holes for mounting the relays?
     
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  19. jct

    jct Senior Member FCBO Gold Member

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    Yes
     
  20. mr. fix it

    mr. fix it Old Man with a Hat

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    Me too