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H4 Headlights direct plug and Play or need harness?

Discussion in '1st Gen. Tacomas (1995-2004)' started by Brojohanson, Aug 22, 2021.

  1. Aug 22, 2021 at 6:25 PM
    #1
    Brojohanson

    Brojohanson [OP] Well-Known Member

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    One of my headlights went out and looking to upgrade from OEM. Finding conflicting information about this and a lot of the links I found to these harnesses are for a 2nd gen or the link is broken. Anyone have information on the H4 upgrade for 1st gens?
     
  2. Aug 22, 2021 at 6:39 PM
    #2
    Digiratus

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    I have read that headlight services makes a plug and play wiring harness upgrade kit for us so we can run the high output H4 bulbs in our OEM housings. The only challenge is to first deterine if you truck uses a 'ground switched' system or not.

    I know this is a 2nd gen thread, but there is a ton of info in it that also applies to 1st gens.

    https://www.tacomaworld.com/threads/the-ultimate-headlight-upgrade-h4-not-led-or-hid.398066/

    More 1st gen specific:

    https://www.tacomaworld.com/threads/proper-headlight-upgrade.407879/
     
  3. Aug 22, 2021 at 6:46 PM
    #3
    Digiratus

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    An except from the first post in that 2nd gen thread:

    Determining your electrical ground system:
    Toyota previously has produced their trucks with ground switched wiring. I’ve done this upgrade on my 3 previous Toyota trucks (89, 94, 03) I’ve owned, and all have used the ground switched wiring. Ground switched is when power is always constant and the ground is completed to activate the circuit, vs conventional the power is completed to activate the circuit. I originally ordered the ground switched harness but it did not work on my 2015 Tacoma. After emailing rallylights.com, the guy that built my harness sent me the following test info, which led me to conclude I actually had conventionally switched wiring.

    Ground Test Procedure:
    -Looking at the back of the factory Toyota H4 headlight connector, as installed, the outside two connections are vertical & the top connection is horizontal.
    -The left connection, when viewed from the back, is the "common" H4 connection.
    -On a Ground Switched vehicle, the left connection would have +12 volts (in relation to ground) as soon as the headlight switch is turned on.
    -On a Conventionally Switched vehicle, the left "common" connection would ground directly to the chassis and would not have any measurable voltage present. Note that you are looking for 0v vs 12v+. A measurement of 0.xxv is noise and should be considered 0 for the purpose of this test.
     
    chrslefty and Tacotj like this.
  4. Aug 23, 2021 at 9:14 AM
    #4
    Brojohanson

    Brojohanson [OP] Well-Known Member

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    I'll take a look. I was going through that thread, must have missed that part. Appreciate the find.
     
  5. Aug 23, 2021 at 9:45 AM
    #5
    Brojohanson

    Brojohanson [OP] Well-Known Member

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    Have you done the swap before? I cant seem to find any H4 85/80w bulbs available anymore. I do see H4 100/90w being sold but not sure if the wiring harness available is going to be able to handle the additional wattage.
     
  6. Aug 23, 2021 at 10:08 AM
    #6
    Digiratus

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    Brojohanson [OP] likes this.
  7. Aug 23, 2021 at 10:21 AM
    #7
    Wulf

    Wulf shitbox shitpost

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    Alrighty, this is a fun one! I went through this many years ago when I converted to e code H4 housings with Hella 110w bulbs. Even though the sealed beam and the H4 bulbs use the same connector they do not have the same wiring. You need to swap two of the wires:

    [​IMG]


    Verify with a multimeter but this should put you on the correct path. Instead of cutting the factory harness I added a H4 relay harness at the same time to support the larger draw of the bulbs and it was pretty painless to repin the connectors and get things working.

    Here's the harness I used: https://www.amazon.com/Octane-Lighting-Automotive-Headlight-Foglight/dp/B00BMN30HY

    Side by side: Sylvania sealed beams vs Autopal e-code H4 with autopal bulbs.

    [​IMG]
     
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  8. Aug 23, 2021 at 10:46 AM
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    Brojohanson

    Brojohanson [OP] Well-Known Member

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    Awesome. These are the same bulbs I was looking at. I'll probably end up going with these. Thanks!
     
  9. Aug 23, 2021 at 10:47 AM
    #9
    Brojohanson

    Brojohanson [OP] Well-Known Member

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    This is the first im seeing about having to adjust the wiring harness. Is this due to you going to e-code? What year was the truck you did the swap on? I am working on an 03.
     
  10. Aug 23, 2021 at 11:10 AM
    #10
    Bubba’sTaco

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    Just FYI, from what I’ve read, for best performance you’ll want to replace the headlight housings as well. The old housings are specifically designed to reflect halogen bulbs so the LED’s don’t work that great in them. They’re brighter, yes. But they don’t “throw” the light very efficiently. So your night time vision won’t get any better.

    With that said, they’ll draw less power, so that’s a plus.
     
  11. Aug 23, 2021 at 11:18 AM
    #11
    Digiratus

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    The OP is upgrading his halogen bulbs to higher output halogens. He is not changing to LEDs, he is staying with H$s (9003) bulbs. And aftermarket housings are not better than OEM housings. The OEM housing is by far the better design. The only downside to the OEM housing is when the outer cover starts to yellow with age.
     
  12. Aug 23, 2021 at 11:29 AM
    #12
    Wulf

    Wulf shitbox shitpost

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    My bad, this was on my 96. It was not e code, the H4 bulb and factory sealed beam bulb had different pin out as shown in the pic.

    The information may not apply for newer trucks
     
  13. Aug 23, 2021 at 11:29 AM
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    Bubba’sTaco

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    My bad. Not sure why I thought “LED” when I saw “H4”.

    Wasn’t saying aftermarket is better than oem, just saying I’ve heard that it’s better for LED’s. Is that not true?
     

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