headlight fix?

[ShaneLovesDatsuns]

Hi, I have another post, sorry to flood. But I'm hoping this will be a simple fix. My lights all work fine. However, when I try to turn my "low beams" nothing happens except my secondaries come on. No tail lights or low beams. So I have to have my brights on all the time. Not a huge deal just wondering if there's a simple fix.

[DanielC]

What do you mean by "secondaries"?

 

Datsun 521 trucks had at least two different fuse boxes, that I know of.  One fuse box had three always hot fuses, and the other fuse box had four always hot fuses.  The three hot fuse boxes had one wire to the light switch, and the light switch turned on the smaller lights in the first position, and in the second position, all the way out, turned on the headlights in addition to all the other lights.   The four always hot fuse fuseboxes had two wires and fuses going to the light switch, one for tail lights, and the other for the headlights only.

 

Lets do basics first.  Are the fuses good?  You have to check with a test light to see if you are getting power on the cab side of the fuse box, with the light turned on.  Glass tube fuses can look good, but still be bad.  Are the low beam headlight good?  They both could be simply burned out.

 

Here is an electrical diagram for a 521.

 

Here is a lights only electrical diagram.

[datzenmike]

The hi low switch only affects the headlamps so if the tail lamps turn off when switching to low beams, a previous owner has messed with something in the wiring.

 

I believe the 521 is similar to the 510 for hi low operation. You must have running or parking lamps or the relay stays in it's default position. As the relay can only be in either the hi, or the low position, the 'off' or rest position is hi beams. Without parking lamps on the relay cannot be moved from the high beam position.

 

What are the secondaries?

[DanielC]

The 521 headlight circuit does not need the parking light power to operate the headlight relay.  Power from the headlight switch, is applied to both the relay coil, and the moveable contact in the relay.  The normally closed contact then passes the power to the low beam headlights.

The headlight relay coil is grounded by the turn signal switch, on the steering column, and then switches to the normally open contacts, and that contact is connected to the four high beam headlights. 

The headlights are grounded by a wire, that goes back to a voltage regulator mounting bolt.

 

But if I need a transmission identified, Mike, you are the man.

[ShaneLovesDatsuns]

Oh yeah then the someone has definitely tampered with it. When I pull half way for lows, only the little fog lights come on, then I pull all the way and I get every single light on the truck on. And it's either all on or all off basically.

[banzai510(hainz)]

what you mean fog lights? Lights on bumpers that where added?

 

maybe soembody just swap the highbean commnector to the low beam side lamps.

[ShaneLovesDatsuns]

Yeah they aren't really fog lights. They are just the mirror rectangular reflective yellow lights on the front. And yes there has definitely been someone fooling around with wiring.

[datsunaholic]

I'm still confused.

 

The pull knob is for parking lights (first detent) and parking lights + headlights (second detent).

 

High/Low is activated by the turn signal stalk, but ONLY when the headlight switch is in the fully pulled (second detent) position.

 

If someone screwed with the wiring to add fog lights and disabled the parking lights then you need to take the wiring back to stock or at least trace out where things have been modified, but there's no way to tell over the internet what's been mucked with.  It's a search and destroy mission, and the wiring diagram above is your map.  Good luck.

[datzenmike]

 

But if I need a transmission identified, Mike, you are the man.

 

Have diagram marked 521 but it's a 620. Haynes manual... figures. I Xed it out and wrote 620 in BOLD.