Replacement Headlight switch

[1970 Datsun]

Have a '70 pickup 521. I have posted on this forum before with pics, but been so long since I came back I had to re-register. Will throw pics back up once I get the lights back in shape.

 

When I searched the topic found more info on none working headlights vs. my trouble of "Over-working" headlights.

 

So all lights work with the exception of pass. side markers and reverse lights which need new housings so for now they are disconnected and taped up. Then one morning lost headlights all together and found I blew a fuse on fuse box....upon replacing fuse/cleaning fuse box contacts noticed when lights were on fuse got super hot really fast. Figured got a short so i started witch checking continuity on light switch. There I found out orig light switch had been replaced with $3 two position switch from a part shop. It's the basic 5 post with 15a fuse built in power post, park post, headlight post and two tail light post. Here is were I found first problem:

 

First owner unplugged stock headlight switch from wiring harness and connected 5post aftermarket switch with just some wires with the proper male and female wire connectors. The stock wire harness has a 6 pin harness with the headlight, tail light, power and relay pins along with two empty spots. but he connected the new after market switch with one wire from power slot to post on switch one wire connecting headlight slot to proper post on switch and one wire connecting taillight slot with proper post on switch, however, the relay slot was left empty.

 

 

after reading post by ???Daniele C??? about the 521 headlight wiring I figured the lack of the relay switch being in the circuit now is leading to the over heating, blown fuse and over heating/blown fuse of the after market switch.

 

Just recently I changed to a job which requires a longer so commute so I am assuming the lack of drive time before was enough to allow me to use his wire setup without a blown fuse, but now for whatever reason it's popping them.

 

with aftermarket switch I get continuity power to taillight post and cont. power to tail to headlight when in respective positions. Before the fuse blew I had fully working head, tail, marker, instrument, stop and high beam light. I am thinking my issue with the overheating fuses is the lack of relay in my circuit and I just need to wire it in. I am just trying to figure out how to wire it in with existing aftermarket switch or do I only have the option of buying a harnessed switch for like 80 bucks? Or is there some other option?

 

Any help would be appreciated sorry for the length wanted to make sure I fully explained what I have seen and done

 

 

James

[datzenmike]

Hot fuse is almost a bad contact between it and the clips that hold it. The heat removes the temper and the clips don't grip as tight, which just adds to the problem.

 

I would try to get a stock headlight switch and hook up right. The 620 headlight is also a 6 wire switch and though not an exact match could maybe be grafted onto the 520.

[1970 Datsun]

Thought about the rust build up so I did use a file and clean up both the fuse box and light switch fuse post. Same results, but the light relay for now is not wired into my light circuit at all from the headlight switch. Does anyone have a diagram for how the original head light switch should be setup for testing? It seems like the fuse box provides power to the switch then when turned on the switch powers the relay which in turns powers the tail/head lights????Right now its seems I am running power straight into the head/tail lights bypassing the relay all together which seems to be overheating the circuit.

 

anyone have any ideas how I can setup the wires so i can at least use the lights for now untill I can hunt down a new switch or figure out how to make one up?

 

[1970 Datsun]

I have a topic started in the electric forum on my head light switch problem, but I was wondering if anyone knew of a replacement head light switch setup for the '70 521 or maybe even how to wire up the relay, power, tail and head lights on the cheapo after market two position switches?

 

thanks

\

james

[67411sss]

I have a NOS 411 6 prong one if that will work...

[Chris Haines]

i can send you pics and how too on what i did with my 70 521???

[banzai510(hainz)]

510 lights are wired to the battery positive. so when switch is pulled it completes the circut by putting a ground on there. The relay workes when in the HIGH position.it puts 2 grounds on the Light circut.

However I forgot the 521 might be different.might be switchable power

 

But most times (99percent)its corrossion clean everything.

 

if you have LOW beams but no lights at all on HIGH then its the relay.

[DanielC]

The original 521 light switch had two separate fused circuits going through it. The headlights, on one circuit, and fuse. Tail and side marker lights on another circuit and separate fuse. The turn signals, and reverse lights were on another fuse, and stop light are on a different fuse

Power for the headlights comes to the light switch on a thick red wire, and goes out on a thick red with a yellow strip wire.

The marker, and taillight power comes to the light switch on a red with a black stripe wire, and goes out on a red with a blue stripe wire.

[1970 Datsun]

Thanks for the replys, guess I gotta head back to the fuse block and try cleaning everything up better. Will update after rust removal is over.

 

 

james

[1970 Datsun]

i can send you pics and how too on what i did with my 70 521???

 

 

Looks like I need to still work on some rust from what I found out from the other forum, but the pics would help out a lot once I get done cleaning the contacts.

 

james

[Roadracer Al]

If you're trying to resurrect the OEM fuse box, I'd recommend that you skip it and buy a modern ATX/ATC type (two-prong plastic fuse) fuse box. I scored one years ago @ West Marine w/10 circuits for about $20. IMHO, a dodgy fuse panel will make a truck unreliable.

 

Here's one for $10 that would be good for the Datsun, and they can be had with fewer or more circuits:

 

http://www.wiringproducts.com/contents/en-us/p348.html

[nukeday]

My thread has about 4 pages of wiring junk for a 521. My truck had the fuse box actually hacked out when I got it. I'll try to save you wading through all the disorganized troubleshooting.

 

The stock fuse block is fine. The circuit is designed to power the tail lights and provide input power to the headlight relay, then pass this through to either the high or low beams. The tail light portion is run through the switch, the headlight portion through the switch and a relay, both circuits are fused, as mentioned by DanielC.

 

Remove the entire fuse box, drop it in lemon juice for 1/2 an hour. The fuse panel sits too low in stock form IMO, water can sit in the tray underneath and cause all sorts of havoc. Dry it out, and reinstall using some cabinet door 'bumps', like this:

 

 

From my experience, if your dash harness has a 6 prong connector it was designed from the factory to support the optional fog lamps (L521). You only need the 4 wires you've already identified. Download the wiring diagram pdf files from the620, I'd recommend getting both the L521 and PL521. The 6 prong light switch is shown clearly in the L521 diagram.

 

 

To replace the relay, you'll want to make sure you have one that is rated for constant power. An off the shelf Bosch unit is fine. The footprint is different, obviously from the stock one. Make sure the headlights are grounded well, if you've upgraded the alternator and removed the VR, make sure the loop of black wires (which normally is held down at the VR) is bolted down and clean. There are only 4 wires going to the stock headlight relay, you've already identified them. As you can see, if the headlight switch has problems, then you introduce issues with the load across the switch. Normally the current is absorbed in the relay, not the switch. So, the switch overheats, and pops the fuse.

 

It sounds like the headlight switch you've got is fine, but put a relay back in, actually put two in. This diagram removes direct power from the switch and provides it directly from the fuse box. Leave the switch like it is, and use the RY wire as the trigger for the headlight relay. Cut the RY wire (under the hood) and put the switch side wire on pole 86, and the headlight side on 87. Run a ground to 85, and add a second wire from the light fuse on the fuse box to pole 30. The switch then becomes the trigger for the relays. Repeat this procedure for the LgW (high beam) wire and you should be all set. The high beam trigger is not part of the light switch, it's in the turn signal switch.

 

The wiring colors are different in the below diagram, but it's a simple circuit. Really!

 

 

Good luck. If you put the two relays in, you'll probably never have to mess with it again. Make sure the tails are grounded properly too!

[nukeday]

*snip* ... It sounds like the headlight switch you've got is fine, but put a relay back in, actually put two in. This diagram removes direct power from the switch and provides it directly from the fuse box. Leave the switch like it is, and use the RY wire as the trigger for the headlight relay. Cut the RY wire (under the hood) ... *snip*

I had a lot going on in the immediate area when I wrote this up. You don't actually have to cut the RY wire. Wherever it's spliced into the headlights (circumventing the relay), you should be able to just separate the two wires and insert the relay per above. The ground for the relay is not the ground through the headlights. In order for the trigger to work, you need a ground at the relay itself.