Electrical Help Please!

[Mycroft]

Can someone please help me with my electrical problem. 

 

I keep blowing a fuse running my head lights.  I disconected everything else but the headlights.  I'm running a wire stright off the battery to the fuse box, like in the diagram.  The fuse that keeps blowing is the 10 A fuse connecting the black wire from the battery(+) to the red-black wire that runs to the light switch?  I checked for shorts but I didn't find anything.  I replaced the old red-black wire and the fuse lasts longer but it still gets hot and blows.  I'm at a loss here, someone throw me a bone! 

 

diagram --> http://community.ratsun.net/topic/50160-datsun-520521-pickup-wiring-snag/

 

 

 

 

[datzenmike]

Are you running newer halogen headlamps?

[mklotz70]

You'll want to do the relay upgrade.  Our truck used to do the same thing.....even with sealed beams.

 

http://community.ratsun.net/topic/65216-521-headlight-relay-work-around/

 

http://community.ratsun.net/topic/2105-datsun-faq-frequently-asked-questions-look-here-first/

[DanielC]

Stock headlights are 37.5 watts each for the two high beam lamps, and 50 watts for the high beam part of each low/high lamp.   When you have all four high beams on, that is 175 watts total.

Watts is volts times amps.  If you know the watts, (175) you can divide that by the volts (12) and that give you 14.6 amps.  The 10 amp fuse should blow.

 

The 521 trucks I have seen, and I have five myself, have a solid red wire on the headlight fuse.  This wire goes to the light switch.  Headlight switched power is a red with a yellow stripe, and goes from the light switch to the headlight relay.  From the headlight relay, the red with black stripe wire goes to the two low beam lamps, the red with white stripe wire goes to the four high beam lamps.  There is a black ground wire on the headlights, that wire goes back to a lug clamped to the inner fender, at the voltage regulator.

[datzenmike]

And that's at 12 volts. When charging it's closer to 14v.

[banzai510(hainz)]

clean the connections first at the fuse holder and the wire connections.

[Mycroft]

Thanks for the help to those who posted on this thread.  I got my headlights working good enough for now.  My headlight fuse gets warm on low beams and takes a while for the fuse to blow with the high beams.  Good enough for around town.  The problem now is that the warm fuse speeds up corrosion of the contacts and they need to be sanded down every so often.  Anyways, I found a Datsun 510 and PL521 Pick-up Owners Workshop Manual 1968 thru 1973 (ISBN 0 85696 123 X).  It has a very different electrical diagram than the one floating around here on the forum.  Here is a link to a site to buy the book --> http://www.isbns.net/isbn/9780856961236.  It's quite cheep.  I found mine in the bathroom on the book self at the scrap yard.  I payed $10.00 .  Good luck with your truck! 

[datzenmike]

Probably for a 620.

[datson4life]

Sounds like better/cleaner grounds are needed if getting warm and blowing every so often

[Charlie69]

Download this 521 Factory Service Manual and save your money.

 

http://datsun510.com/manuals/Service_Manual_Datsun_Pick-Up_Model_521_Series_Chassis_and_Body.pdf

[datzenmike]

Get relays and 12 gauge wire and a larger fuse. Use the stock wiring for the hi/low signal and the relays to run direct power from the battery. Brighter lights because the wire runs are shorter and heavier gauge and a larger fuse that does not blow. There are kits or do it yourself.

[banzai510(hainz)]

I installed a H4 harness and just used the stock outer lamp connoctor as the trigger to plug in the new harness and works fine.

521 s are switchable power so i had to swap the jumper on the new harness.

 

 

its corrossion on in the fuse box. thats your proplem or the connections  clean all connections

[DanielC]

This is a picture of a mostly stock 521 fusebox.  Notice the thick white wire coming from the battery, to the fusebox.  It is in line with the headlight fuse, and on the far side of the fusebox, the headlight power wire is a thick red wire, it goes into the wire harness, and the harness goes into the cab.

In the cab, the red wire goes through some connectors, to the light switch.  Switched headlight power comes back out into the engine compartment, on a thick red with a yellow stripe wire, and that wire goes to the stock headlight relay.  The stock headlight relay normally connects the red with a yellow stripe wire to red with a black stripe wire, and that powers the low beam headlights.  Inside the headlight relay, the red with a yellow stripe wire also connects to the relay coil.  The relay coil is grounded by the high beam switch, on the turn signal arm.  When the relay coil is grounded, the red witha yellow stripe wire connects to the red with white stripe wire, and that wire goes to all four high beam headlights.

 

I have added an extra relay to the headlight circuit.  This relay needs power supplied to it.  The orange wire, with an inline fuse supplies power to the extra headlight power switch relay.

 

The blue relay in this picture is the added relay.  It is just a standard cube "Bosch" relay.  The orange wire, coming fron the inline fuse, goes to pin 30 of this relay.  Pull the red with yellow stripe wire off the stock 521 headlight relay, and plug it to pin 86 for the new relay.  Ground pin 85 of the new relay.

make a shore jumper wire, and connect pin 87 of the new relay to the empty pin on the stock relay you ulled the red with a yellow stripe wire from.

 

Adding the second relay takes headlight current out of the stock 521 fusebox.  The fusebox runs a lot cooler. 

The second relay also shortens the headlight circuit power wiring several feet, and removes several electrical connectors.  This allows more battery voltage to reach the headlights, and they are brighter.

If you lose power to the headlight switch, you can take the added relay power (orange) wire, and plug it on the stock headlight relay, where the red with a yellow stripe wire was, you have headlights to get home with.  If the extra wiring and relay mess up, you can just plug the red with a yellow stripe wire back on to the stock relay, in it's stock position, and that will work.