Headlights not working

[Davidm]

Hey 

I own a 72 Datsun 620. I’ve been having this recurring problem where the headlights never work right. The high beams have never worked. Every time I try to turn them on nothing comes on. The markers on the side work and one on the lower valence works. The rear taillights work until I press the brake. Then the right one goes out. 

Just went to drive it this morning and my headlights and high beams won’t come on. 
I was wondering if anyone would know what the problem could be. I know there’s a relay close to the battery that controls the high beams and headlights but the one on the other side I’m unsure about. I’ve taken out the relay and cleaned the contacts and that got one light working. Just wondering if there’s a way to get the all working correctly. 
 

Thanks

Davif

[Davidm]

I was looking at some other posts on this topic. It seems like the whole church it for the headlights is pretty shitty.

There’s a few people saying an H4 harness would work if I were to redo it. but I don’t exactly know how to hook it up. 
I’m looking at this one. Was wondering if this will work. 

https://a.co/d/4Al4Pt0

 

 

[SWFL]

Bypass the old cruddy high resistance contacts in the switchs, by using a harness with relays. The original harness, just triggers the relays, that handle the high current load directly from the battery to the lights. The hardest part is finding 5/16" female spade connectors. I use 10ga wire. You'll probably need to clean up the switch contacts enough to work the relays.  

[Davidm]

I was also curious would the blinker switch have any effect on this problem?

[datzenmike]

They are mechanically but not electrically connected. I don't think so.

[Davidm]

On 4/10/2023 at 1:22 PM, SWFL said:

Bypass the old cruddy high resistance contacts in the switchs, by using a harness with relays. The original harness, just triggers the relays, that handle the high current load directly from the battery to the lights. The hardest part is finding 5/16" female spade connectors. I use 10ga wire. You'll probably need to clean up the switch contacts enough to work the relays.  

Ok so I got the new harness

It has two of the h4 connectors for the lights. Then also one male connector. It says I need to connect that one to the closest headlight plug. Is that just one of the plugs that originally connected to the headlights?

You also said I needed the female spade connectors. Are those for this male plug? 
Sorry I’m a newby to this. 

[SWFL]

A full light harness or a kit you have to assemble?

 

The new thicker wires with the four ( 2 hi/lo & 2 hi ) H-4 female plugs go onto your old headlights. There are 2 trigger wires for the 2 relays, one for the lo beam circuit and one for the hi beam circuit. The thick feed wires for the relays connect to the + of the battery and a good solid ground source. 

[Davidm]

The one I got is already assembled but it’s only for the headlights. It works but I’m going to find one with 4 for the high beams as well. It came with the female connectors.  Went through the whole circuit and cleaned everything up including the relay that’s for switching between hi and low. 
I got everything working.
 

Do you know if they make a relay as a replacement for the old one that’s on there? Or should I just put my own on. 
I’m guessing it automatically feeds power to the headlights and then when I switch to hi that opens the headlight contact and closes the high beam contact. It’d be nice to have both at the same time. 

[SWFL]

The new harness didn't include a new relay, to take the load off the original headlight switch and or relay?

 

You can wire up the system to have the low beams on at the same time as the high beams for extra output, but that's not legal and risks blowing the bulbs from too much heat and stressing the wires and relays if they are not sized for it. Remember that unless you have upgraded, your alternator is only 35 amps.