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510 headlight relay How-to upgrade/repair

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i will start off with saying this is the way i did my headlights, im sure there are better and worse ways to do this. some may not agree with some of the ways i went about it.





So to start you need relays and inline fuse's, for the relays you need the ones that will have 5 tabs  numbered 30, 85, 86, 87, 87


i used these ones DSC_0468.jpg





i spliced in the two fuse's, onto a 8g bat. cable, used a piece of copper tubing as a crimp, and soldered the connection 







the two inline fuse's will supply the new power to your relays. you want to connect them, to the tabs that have 30 next to them.







this is where some may disagree, i replaced the old harness wires with newer thicker wire






there is now a dedicated ground at the headlights on both sides 






the way this is set up, is your using the old relay to trigger the new relay's



and in turn the head lights now have a dedicated power source. with less resistance (i think)






some reading from dan C.


 You will be using the stock wiring to trigger the new relays.  I suggest yo do not modify, or cut the stock wiring.  That way you can go back to stock, if there s a problem, or if for example, you were to enter the car in a concourse type of car show where "factory stock" is a bonus.


   I am going to suggest using two headlight plugs from the original harness to trigger the relays.  Find the headlight plug, with only two wires on it.  The wire colors will be Red, and Red with White on the right side of the car.  On the left side of the car, the wire colors are Red with Blue, and Red with White.

    Disconnect the negative battery cable before working on the wiring.

    Run a wire from the Red wire, or the Red with Blue wire to pin 86 of the relay you add.  This is the high beam relay.  This wire can be thin. 16 ga or even smaller is OK. 

    Run a wire from the Red with White stock wire to pin 85 of the same relay.  With the battery connected, this relay should click when the high beams are on.


   Disconnect the battery again.


   Go to the three wire headlight plug.  Run a wire from the Red wire, or the Red with Blue wire to pin 86 of the second relay you add.  This is the low beam relay.  This wire can be thin. 16 ga or even smaller is OK. 

   Run a wire from the Red with Black stock wire to pin 85 of the second relay.  With the battery connected, this relay should click when the low beams are on.


   You then need to supply headlight power to the new relays.  Use at least 12 gauge wire for this.  From the battery, or the big cable on the starter, to pin 30 of both new relays.  Then run 12 gauge wires to new headlight sockets, new high beam relay pin 87 to the high beam on all four headlights.  Also run 12 gauge wire from new low beam relay pin 87 to the low beam terminal on two high/low headlights.


   You need to run a 12 gauge wire ground from the new headlight socket to the bolt that holds, or did hold the voltage regulator to the inner fender.  If you "Y" the two headlights on each side together, and then "Y" those two wires, I would suggest you go up to 10 gauge wire for the single wire run back to the voltage regulator mount.


  Put a fuse in your power wire that goes to your two new relays.


There is a lot of words in the explanation.  It is clear to me, buy may not be as clear to you.  If you have questions, feel free to ask.


By wiring the new relays the way I suggested, you should be able to leave the stock wires in place, and in use, until every thing is in place and wired, and then just unplug two headlamps for the stock headlight plug, and plug in your new headlight plug, to the headlamp, and then plug three wire in to the stock headlight plug, to activate the new relays.





without the help from dan it would have been a nightmare for me trying to figure this out 



thank you

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high beams










low beams




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Upgrade? repair? maybe mention in the title so the search function will find it for others wanting to do the same.

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Dont you think just getting a H4 harness and hooking it up to the stock passenger plug woud be ezer???????

victoriabritish.com has them for 20$ call them ask for swictable ground harness 15min install


get some heat shink over the whole female connector also so the metal is not exposed under the BlackRelays. they make waterproff versions

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so by doing this upgrade there will be a total of 3 relays for the headlights?  the way i am understanding it is that the original relay stays connected and the new ones are triggered by it downstream.  I am not good at electrical so i might be misunderstanding this. 

  i thought that doing the upgrade would eliminate the original relay.

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3 relay is for the 4 lamps set up.

Most people just get the 2 lamp set up as most driving is on low beam. to get full use of the 55watt low bulb.

then on HIGH yu use the 60watt side of the bulb(outer lamp) stock its still only 35watts.


the inner lamp is already 50/55watts so dont really need a relay for this unless you going to go more WATTS.



so if you lights work fine now just get a 2 lamp set up for the outer lamps. Youll still use the stock relay but its more used as a low current trigger switch to trigger the new relays.


this will have 2 black box relays ( order a switchable ground.)


1 relay for low

1 relay for High



use passenger side plug to plug in realy harness.

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so i just unplug the plugs from the passenger side plug and tap into those for the new relays.  and thats it?  no cutting or splicing right?   

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