I need some headlight help

[Patcon]

I am hoping my scan is legible enough. This is the factory manual... I can probably enlarge parts if I need to. We are trying to get the light's working on Cody's wagon. Most of the running lights seem to work and the turns supposedly work per Cody but I haven't checked behind him yet. The problem is the headlights. He said they worked once and then not again. I have done some testing with a meter and both sides of the high beam lamp have battery voltage, that doesn't seem correct. I would think one would be power in and one would be ground. How can I have voltage on both sides?

[siteunseen]

Possibly in the combination switch?  I have know idea but they do power through there and arc a little when turned on causing carbon build up.  That's why I'm limiting my night driving until I get Dave Erwins headlight upgrade.

[siteunseen]

The repair article I found, http://www.kamikazeracing.org/dl/ZTech/Rebuild_240Z_combo_switch.pdf

[Patcon]

Cliff,

Thanks for the article, but 510's don't have a combo switch. They have a pull switch on the dash and relay (who knows where). There also must be power through the turn signal switch because I believe that controls high beams...

[SteveJ]

I can try to break down the circuit for you.

The green/blue wire comes into the headlight switch. When the switch is in the #2 position, you should have 12VDC on the red/yellow wire coming out of the switch. That wire goes to the fuse box where it connects to the left and right headlight fuses. The left headlight fuse comes out to a red/blue wire. The right headlight fuse comes out to a red wire. They go out to their respective headlights. The red/black wire is for the low beams and goes back to the headlight relay. The red/white wire is for the high beam, and it also goes back to the headlight relay.

The positive for the coil voltage is green/blue. The negative for the coil voltage is black/red. The black/red wire goes to the turn signal switch where is open or connected to ground, depending upon the switch position. When the coil is de-energized, the red/black wire is grounded, finishing the circuit for the low beams. When the coil is energized, the contacts connect the red/white wire to ground.

So, if the headlight switch is on with the turn signal switch on low beam, how could you see 12 VDC on both sides of the high beams? If you don't have the ground at the relay, you only have potential voltage. The headlight elements acts as a piece of wire and not a load. That's why you see voltage on both sides. The voltmeter has significantly higher resistance compared to headlight element.

[SteveJ]

I also sent you a text.

[Patcon]

Thanks for the help Steve. I will start from there...

[Patcon]

Ok, so I worked on this some more today. Some previous owner has been under there hacking it up... 

Here is the homemade choke relay that is evidently always hot!! straight to the battery...

I tried to upload some more but it is giving me an error...

I pulled the factory headlight relay that is on the rear side of the passenger side strut tower on the inboard engine side. There are two relays there, I don't know what the other one is yet. I removed all the nasty sticky electrical tape that someone wrapped the harness in and found some melted wires. I will try to post pictures later...

I traced the 2 black wires through the harness after I unwrapped it. I found a factory bond a little bit behind the battery. It looked good, like brand new. Took a meter and rang it out from the relay plug to the battery negative. Good continuity. so then I made a jumper wire out of a piece of 12ga solid copper. I tested the plug before jumpering it. With the headlights on I have 12voltls on the Red w/ White. I believe the high beam switch is the turn signal stalk. It moves forward and aft and stays in either position. Can somebody verify that. I couldn't ever get 12v on the Red w/ Black by itself. That may be a function of the relay. When I jumper between Black & Red w/ White I get headlights (High beams)

When I try to jumper between Red w/ Black and Ground I don't get low beams. I need to double check the low beam filaments are good. I don't remember if I verified that with a meter.

So at this point I believe the relay is bad. Was gonna replace that and see if I can get them to burn...

Does that make the most sense or should I rework them now to reduce the load on the switches? @SteveJ

[SteveJ]

Give me until sometime on Sunday to write up some advanced diagnostics for you.

[Patcon]

that would be great Steve

[SteveJ]

To ensure you have good voltage, I suggest hooking up a battery charger to the battery and set the charger to the lowest setting. Please record your steps and your meter readings. It's tedious, but it helps with diagnostics when I can't see what you're doing.

First, remove the relay from the wiring harness.

1. With the headlight switch on, at the plug for the relay, check voltage from the RB wire to ground. You should see 12 VDC (or whatever your battery voltage is). Also measure voltage from the RW wire to ground. You should also see 12 VDC.

If you have voltage on one wire and not the other, check continuity from the headlight plug to the relay socket on the wire without voltage.

You might also use an ohmmeter to look for resistance across the headlight elements with an open line/infinite resistance indicating a bad element.

2. Pull the fuse for the right headlight. Recheck voltages. Put the fuse back and pull the left headlight fuse.  Recheck voltages. Also while the fuse is out, check it for continuity, just to make sure the fuse is good.

These circuits are designed to backfeed between left and right on a blown fuse. That can make diagnostics tricky.

Once you have determined that the wiring is good up to the relay socket, you can turn off the headlight switch and jumper the RB wire to ground. Turn on the headlight switch. If you don't have low beams, pull the headlights and check for continuity between the pin for the RB wire and ground. Also check the voltage between the positive pin on the connector and the RB wire. Report the results.

Repeat the process above with the RW wire. Remember that you have to pull all of the headlights when you want to run the meter checks.

If we can't figure it out the go-around, heck, I might just drive up there in a couple of weeks.

 

[Patcon]

I will print this and try to run the tests on Saturday and report back...