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Poor headlamp output on a ‘66

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Hi all,


Am a Buick guy helping out a friend with a nice Springtime Yellow ‘66 Mustang who won’t drive after dark because of the poor headlamp performance. Standard sealed beams at present which should be adequate and changed for Australian road rules.


I have suggested relays to improve it but will do the necessary tests for ground issues and voltage drop first.


1. Has anyone here fitted relays to a ‘66 that could send some photos?


2. Would someone be able to post a wiring diagram as not sure he has a shop manual?


Thanks in advance

Rodney 😀😀😀😀😀😀😀😀


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I installed halogen sealed headlamps on my 54 and 60 Buicks.  No relay.  The 54 lights are now fantastic. First time I hit the high beams I couldn't believe the brightness. Nothing went up smoke after driving it with high beams on for an hour. The 60 nighttime driving is much improved with halogen sealed headlamps as well.  I used Wagner headlamps. Amp draw as advertised looked good. I ran with it. 

  • Haha 1
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Nothing matters as much as voltage at the bulbs.


Well, that and the quality of the reflector, but in a sealed beam system there's nothing you can do about a marginal reflector except replace the bulb.


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There is a very inexpensive headlight wiring kit available on the internet.   They make the kit for 2 and 4 headlight cars. 

You unplug the existing headlights and plug in the kit connector. 

plug the original connector into the wiring kit. 

attach ground wire in kit to good ground. 

Last... need 12v source for wiring kit.

The advantage is it takes the load off the headlight switch .... with kit, headlight switch picks relays in wiring kit and you get a good 12v source to the headlights. 

It also makes it safer to install halogen bulb or other high current bulbs because the harness is bypassing the headlight switch and old wiring. 

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  • 3 weeks later...

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