Headlight polarity reversed on 1972 510

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RobertMoylan
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Headlight polarity reversed on 1972 510

Post by RobertMoylan » 22 Feb 2015 11:37

Hi everyone,

I picked up some Cibie H4/H1 lights recently. I tested the lights before fully installing the new housing and everything worked great. After mounting the housings, however, I started blowing the headlight fuse. I eventually put my meter across the headlight connectors and noticed the polarity is reversed - the terminal labeled ground has 12V and the terminal labeled drive is grounded. With the Cibies H1 housings, the negative leg of the bulb grounds to the metal housing and the metal housing grounds to the chassis. So, since the polarity is reversed, I'm essentially grounding the positive leg of the circuit which is blowing the fuse. I looked around the engine compartment and the wiring doesn't look hacked up and all the colors match what's on the wiring diagram.

Does anyone have any idea why the polarity would be reversed? This of course was never an issue with the sealed beam lights because the housings are glass so the positive side of the circuit wasn't shorted to ground.

Something else I noticed is that I believe the high/low switch is reversed. I believe the high beams are supposed to be activated by pushing forward on the stalk, but mine are activated by pulling the stalk rearward.

I'm going to keep digging around with my multimeter, but any insight would be greatly appreciated.

Thanks,
Robert

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okayfine
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Re: Headlight polarity reversed on 1972 510

Post by okayfine » 22 Feb 2015 12:31

510's headlight circuit sends 12V+ to all prongs, only tripping to ground though the actuated headlight switch. H1s grounding through the housings have always been an issue.

Highbeam stalk function is normal, per the 510:
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A scan of the owner's manual (and a wiring diagram!) is available at The 510 Archives, with 3.8GB of other Datsun 510 information.
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RobertMoylan
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Re: Headlight polarity reversed on 1972 510

Post by RobertMoylan » 22 Feb 2015 12:37

Thanks very much!

I was just looking through those documents and discovered the same thing about the high/low switch. I'm glad my wiring isn't the issue.

So if this is an issue on H1s that ground through the housing, is there a solution? Can the housings be insulated from the chassis?

Thanks again!
Robert

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okayfine
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Re: Headlight polarity reversed on 1972 510

Post by okayfine » 22 Feb 2015 13:05

Various ways to insulate the housings from the buckets. Depends on what you have at hand. Rubber sheet cut to fit and glued to the housing or the bucket, PlastiDip, etc.
Because when you spend a silly amount of money on a silly, trivial thing that will help you not one jot, you are demonstrating that you have a soul and a heart and that you are the sort of person who has no time for Which? magazine. – Jeremy Clarkson

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Bike papa
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Re: Headlight polarity reversed on 1972 510

Post by Bike papa » 22 Feb 2015 15:09

I have the same headlight setup however I used a dual relay setup where one of the headlight sockets plugs into a "male"socket which fires the headlight relays. I had no polarity problems with this setup. Plus I have full voltage to the headlights.
BP
1971 Datsun 510 2 door
08 VW R32
69 BSA 650 Firebird Scrambler
Too Many Bicycles

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Byron510
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Re: Headlight polarity reversed on 1972 510

Post by Byron510 » 22 Feb 2015 20:35

As Joel notes above - utilizing standard relays is the way to go. In fact there are ready made harnesses on ebay/internet which include the relays, larger wiring and new headlight plugs meant to handle the extra load. This, or making yourself up a new harness, is the way to go.

https://www.google.ca/#q=making+a+headl ... ng+harness

And as Joel noted - the lights have a constant 12v supply always, your relay trips the grounds in the OEM harness. The signal stock only flips the relay - hardly any current present there.

There are a number of ways to wire in relays; 2X SPDT (single pull, double throw) or DPDT douple pull double throw generic relays out there to use. Many come with nice screw mount plugs. If you google headlight wiring - the specs on how to build them are all there. Just separately source the 12V supply though a new fuse holder or fuse block.

Do yourself a favor, though. Don't try and pull big amperage (wattage) through yu old OEM fuse box - it will give. Keep in mind these cars came with 35 watt sealed beam lights, and the wiring really wasn't built to handle much more.

Byron
Love people and use things,
because the opposite never works.

RobertMoylan
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Location: Los Alamitos, CA

Re: Headlight polarity reversed on 1972 510

Post by RobertMoylan » 22 Feb 2015 20:43

Thanks everyone,

I ordered 2 wiring harnesses tonight - one for the H4 and one for the H1 lights. This seems like the simplest, safest and most reliable option. I'll post an update in a few days.

Thanks again,
Robert

RobertMoylan
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Joined: 21 Feb 2015 13:20
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Re: Headlight polarity reversed on 1972 510

Post by RobertMoylan » 17 Mar 2015 10:11

Hi everyone,

I keep forgetting to update this post. The relay harness worked great on my lights. No further need to insulate the housing from the buckets.

Hope this helps someone in the future...
Robert

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