Headlight issue

[koukimonsta]

hey guys new here, recently bought a 85 720 nissan(z24, small cab/bed) but it has been seriously molested by previous owners. sorry for the long read...

 

I made a post in the 720 forum also because i picked up a haynes manual but it does not seem to be correct for my truck. The first thing i noticed was when looking at the plug for the blinker/lights switch. I cannot find a diagram of my plug. which is two rows of 4(8 pins) now the reason i am looking for this is because of my headlight issue.

 

now my parking lights work fine, and so do all 4 lights(tested with another source) when i turn the switch to on position the dash says brights are on. on the drivers side both lights are on(low and bright). now on the passenger side the low beam is EXTREMELY dim and high is not on at all. i have been gogling/searching around. saw a few posts about people replacing the switch. i pulled it apart cleaned the terminals does not seem to be the issue i have. another thng ive read about are relays. can someone explain where these are located and a method of testing? again because i cannot seem to find the correct FSM.

 

when i got the truck the lights were working properly. then i started to look into the wiring and began to see the mess. radio was powered by the turn signal. strobe lights powered by wipers. a serious mess. i also found a bent piece of wire bridging two pins on the connect for the lights/blinker switch(short circuit type thing). unfortunately i was not smart enough to record where it was placed and i removed it because this was definitely not OEM. After that i didnt drive at night for a while and then had this issue. so i am not sure if it is related and if that was the fix. anybody have ideas what it could have been used for? would it make any sense this would be my issue?

 

What would cause the brights to some on when not switched on?

[datzenmike]

First, replace both 10amp headlight fuses in the fuse box. They are the last two toward the front of the truck. This should get them going.(I think it's the front one that's blown but replace both)

[koukimonsta]

First, replace both 10amp headlight fuses in the fuse box. They are the last two toward the front of the truck. This should get them going.(I think it's the front one that's blown but replace both)

 

both are good. checked them first

[datzenmike]

Can't trust them on looks. Swap them and see if the problem moves or changes. Push them in and out several times to clean the contacts.

[elmerfudpucker]

Also check the wire harness by the radiator, sometimes it gets pinched. Also clean the contacts on the relays.

 

And another note, please update your profile and location, one of us may be nearby to help

[koukimonsta]

okay i have done all of the above. swapped fuses and cleaned the relay a bit.

 

and have seen a change. now when i flip the lights on the dash does NOT show brights as being on. (tho they are on and very dim) and headlights are on but also not to their full brightness potential. now when i clcik it into high beam mode i get the same issue as before(only driver Hbeam) and then it stays like this and does not come back.

 

now sometimes this happens sometimes as it used to. so i have not fixed anything yet. i am really wishing i knew how to test the switch itself i feel it may not be good. but way too expensive for a hunch...

[ggzilla]

This kind of problem is rarely caused by the headlight switch, more often it is the wire connections.

 

You can systematically test this. Open the hood and measure the voltage at one of the headlight connectors (while the headlights are on and plugged in)

* Voltage from engine ground to headlight ground should be zero

* Voltage from body ground to headlight ground should be zero

* Voltage from headlight feed to ground should be sames as battery + to -

* Voltage from headlight feed to battery + terminal should be zero

Let us know which voltage is incorrect. That's the wiring you need to clean the connections for.

[koukimonsta]

This kind of problem is rarely caused by the headlight switch, more often it is the wire connections.

 

You can systematically test this. Open the hood and measure the voltage at one of the headlight connectors (while the headlights are on and plugged in)

* Voltage from engine ground to headlight ground should be zero

* Voltage from body ground to headlight ground should be zero

* Voltage from headlight feed to ground should be sames as battery + to -

* Voltage from headlight feed to battery + terminal should be zero

Let us know which voltage is incorrect. That's the wiring you need to clean the connections for.

 

can you please elaborate on engine vs. body ground.

 

as in touch multimeter to engine/chassis?

[datzenmike]

Still sounds like a break or open somewhere in the circuit. A fuse is the most obvious source but any bad connection will act the same. The the plug the headlights connect to can also corrode and not make contact or the plug to the headlights. Try unpluging them several times to clean the contacts.

[ggzilla]

Yes, touch the neg lead of Voltmeter to bare engine metal.

 

Or just go through the connections like Mike recommends. Either way.

[koukimonsta]

lights on, car not running battery voltage is 12v.

 

now when i turn it on so it works "correctly" as i described above. brights are dimmly on....

 

passenger side

low beam-6.5v drive, .4v ground, and 8v in the "middle" wire(not sure of proper term)

 

 

driver side

low beam-10.6v drive, .8v ground, 8v middle.

 

now when i click on high beams(what happens is described above)

pasenger

high beam-2v power, .5v ground

low beam-6v gound,2v drive, .5v middle

 

driver

highbeam-10v power, 0v ground(only correct one)

low beam- 6v drive, 0v ground, .5v middle

 

after this i am almost thinking i would rather re-wire it with a couple new relays...but i would HAVE to tap oem switch since i need that factory feel.

[ggzilla]

A relay is not the problem, but you have bad wire connections. 0.8V on the ground wire is not good.

 

Start by tracing your negative battery cable. It should bolt directly to the engine. It should have a smaller wire that goes to the body, perhaps at the horn bolt.

[koukimonsta]

ground is good. from engine, to chassis, to battery. thers a smaller wire that branches from chassis off to the harness. not sure where it goes?

[ggzilla]

I don't know how the later 720s are set up, but the 1972 1200 is like this.

The small wire is the main body ground.

 

 

low beam-6v gound

If you measure 6V between Battery Neg and Headlight ground (black) wire, that's a problem. The wiring harness black wire does not go through fuses or fusible links, so it should be 0 Volts.

 

You can measure the Voltage drop between battery Neg post and battery terminal, there could be a problem right there. Then measure it between other battery terminal and body gound point (bare metal somewhere other than the engine). continue until you find a 'drop' (more than 0V). When you find it, clean the connection carefully, take both sides to bare metal.

 

Someone might have had your harness apart in the past and twisted wires together (which eventually will got corroded), or it might be dirty connectors somewhere.

[koukimonsta]

my newer truck is different than that but same basic idea.

 

voltage across the batt is 12v. i have been going from neg batt post to different chassis ground points. most are 0v, but some ~.1v. nothing as large as the .8v i fond in the headlight harness.

 

it is definitely a grounding issue that i have but just cannot seem to find a specific point to clean etc....

 

another test i did was when the headlights were on and malfunctioning i ran a wire directly from positive battery terminal to the low beam power input(which was only seeing 6v at the time) once the wire connected headlights properly functioned(low and high) tho when i turned them off i got the EXACT opposite thing i used to have(passenger lights both bright, drivers both dim)

 

so why do i not get 12v to the passenger side headlight power input?

 

EDIT: as i stated in my original post i took out a pice of wire bent into a 'u' from behind the light switch plug(it was a simple bridge) now i used a voltmeter to do some testing to see which one would make sense. basically even at that point(the switch) i am only getting 6 volts out to the low beams. BUT i do get 12v in from fuse box. so use the bridge so that when you turn the switch one click you automatically give 12v to the low beams. i did this and it functioned perfectly for a minute or so. then the wire started to get VERY hot and i removed it. (shorting out)

 

could not find another terminal that would work properly. at this point i know the piece i removed was to fix this issue by some owner. why did that piece not get warm (only difference is that mine was not insulated)