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620 Headlight Relay Rewiring


BEEBANI

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O.k., so after having to replace the fuses on both wires that feed the headlight switch several times, I decided to upgrade the headlight circuit. The fuses always melt, and the original fuse panel on the truck was completely melted away, so a long time ago I upgraded to a blade type fuse panel. I'm sure that going to H3's didn't help matters much either.

 

The stock wiring is a fucking joke, battery power goes into the light switch, then goes to the light relay. The Red/Yellow wire coming from the high beam switch is used as a ground at the relay, and the Red/White and Red/Black wires from the relay feed the headlights.

 

So essentially, there really is no point in the relay other then to trigger the high beams.

 

I added in 2 40A relays and removed the original relay.

I used the RED wire coming from the headlight switch as a trigger wire for both relays.

I ran 2 new wires from my fuse block under the hood which is directly fed from the battery, I attached these to the relays as the B+

I ran 1 new ground wire for the low beam relay

The Red/Yellow wire is attached to the high beam relay as a ground

The Red/Black wire is the feed to the low beams

The Red/White wire is the feed to the high beams

 

Works like a champ, and I will later figure out how to wire a relay into the park light circuit (which feeds all the other lights including the tail lights).

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Originally Posted by jesusno2 viewpost.gif

and no pictures what a douche bag :fu:

 

I actually have pictures fuckface, just haven't loaded them yet. It's pretty simple though, and pics don't help much.

 

Ok when I read this , I actually started laughing out loud and my family started looking at me weird.

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I'm here every day, sometimes twice a day, just hasn't been anything worth commenting on. Lot of newbies these days, lot of the same questions. Haven't worked on my truck much since I've been trying to sell it.

 

But, since I'll have to drive it until someone steps up, I decided to fix some little BS problems that have been plaguing me.

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I'm here every day, sometimes twice a day, just hasn't been anything worth commenting on. Lot of newbies these days, lot of the same questions. Haven't worked on my truck much since I've been trying to sell it.

 

But, since I'll have to drive it until someone steps up, I decided to fix some little BS problems that have been plaguing me.

 

That has happened to me on alot of other forums, i dont think ive ever been able to get past 1500 or so posts.

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Best is to still Buy a cheap H4 wire harness and your done.

15-30 min job and no wire spliceing.

Hook s up to the stock harness and and the other light near the battery is used as a trigger

 

5.75 inch size lights are not that effiencent compared to the 7 in lights and newer housing in the newer cars

 

It only took me about 1/2 hour to do this, plus the half hour it took to put the new fuse block in under the hood (wanted a bigger one).

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Best is to still Buy a cheap H4 wire harness and your done...15-30 min job and no wire splicing. Hooks up to the stock harness and the other light near the battery is used as a trigger

 

It only took me about 1/2 hour to do this, plus the half hour it took to put the new fuse block in under the hood (wanted a bigger one).

 

Well, you're the exception. For most of the electrically challenged, plug 'n' play is easier. Thirty bucks from Victoria British:

 

harness.jpg

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The problem is, with that "plug and play" you're still using the stock wiring under the dash which is the problem. It wasn't difficult, all I had to do was remove the original relay and reattach the wires to new relays, add a couple of wires and bam no more overheating issues.

 

I'll put up the picture in a while, but the relays I added are under the dash on the passenger side where the original relay was.

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The problem with the stock wires is taking the electrical load. When you plug in the harness, the stock part is only telling the new relays to turn on/off. The load that was causing your system to overhead and blow fuses is now carried by wires that can handle it.

 

Granted, redoing it your way is cleaner.

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I don't disagree with the harness, but I would remove the original relay and change up the wires under the dash if you're gonna go that route.

 

The whole circuit is just retarded anyway, they got one 14 ga. wire (green/blue) feeding the park lights, turn signals, brake lights, tail lights, under hood light, dash lights, back up lights, dome light (I'm sure I'm forgetting one) and all running off of 1 sad little glass fuse.

 

That's the circuit I'm gonna tackle next. Wish I had the time and resources to build harnesses for these trucks, all the original wiring is usually tweakerfied by the time we get a hold of these trucks anyway!

 

Wow, that was a post reminiscent of Klotz.....better lay off the caffeine.:)

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Wish I had the time and resources to build harnesses for these trucks, all the original wiring is usually tweakerfied by the time we get a hold of these trucks anyway!

 

luckily mine wasn't "tweakerfied" i only had to repair the heater fan wires. everything else is beautiful. but yes i agree on the lighting system. the wiring on that sucks ballz. soon i will build my own relay ahrness. but that will be a while.

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Wow, that was a post reminiscent of Klotz.....better lay off the caffeine.:)

 

 

LOL....too funny! :)

 

Paula's 521 was melting headlight fuses about once a week before I put the relay mod in. I kept the stock relay....just got the main power from the batt through a blade fuse instead of the light switch. Made the headlights noticeably brighter..................hhhmmmm......too bad I can't get a relay mod for me!!!!! I so need to be brighter!! :)

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IWish I had the time and resources to build harnesses for these trucks, all the original wiring is usually tweakerfied by the time we get a hold of these trucks anyway!

 

Until then, universal harnesses from EZ Wiring, Painless, and few others work great and are reasonably priced. Wish I'd just done that with the 411 in the first place, but live 'n' learn. Definitely going that route with the roadster.

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Well, you're the exception. For most of the electrically challenged, plug 'n' play is easier. Thirty bucks from Victoria British:

 

 

Victoria British is a parts house where I can order one of these?

 

1974 Datsun Truck Headlamp Relay

1974DatsunHeadlightRelay03.jpg

 

1974DatsunHeadlightRelay02.jpg

 

1974DatsunHeadlightRelay01.jpg

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I added in 2 40A relays and removed the original relay.

I used the RED wire coming from the headlight switch as a trigger wire for both relays.

I ran 2 new wires from my fuse block under the hood which is directly fed from the battery, I attached these to the relays as the B+

I ran 1 new ground wire for the low beam relay

The Red/Yellow wire is attached to the high beam relay as a ground

The Red/Black wire is the feed to the low beams

The Red/White wire is the feed to the high beams

 

 

I'm electrically challenged but I could make a trip to NAPA and give this a try...

 

Might have some questions along the way, like will this work for my application? 1974 Datsun Truck?

 

Ugh...

 

Mike

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I'm electrically challenged but I could make a trip to NAPA and give this a try...

 

Might have some questions along the way, like will this work for my application? 1974 Datsun Truck?

 

Ugh...

 

Mike

 

Yes it will work, I have a '73 and I did it.

You don't necessarily have to put a new fuse panel under the hood, it just makes it cleaner.

 

Get some wire, 12ga should work, get 2 in-line fuses (20-30amp), 2 40amp relays, and a few misc connectors.

 

Wire the 2 in-line fuses to the + post on your starter or battery, run those wires to the #30 terminal on your relays

 

For the low beam relay plug the red/black into terminal #87, run a ground to #85, and split the red wire that's plugged into your old relay plugging one lead into the #86 terminal

 

For the high beam relay plug the red/white wire into terminal #87, red/yellow into #85, the other half of your red wire goes to #86

 

The red, red/yellow, red/black, and red/white should be the four wires that are plugged into your old relay, you may need to extend them.

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