Hi, I have a 73 240z with a chevy v8 in it and a GM 3 wire alternator. The driving lights were running fine for a long time, since I put the new alternator in. Yesterday, my driving lights wouldn't turn on and I flipped the switch again and they worked. Today, the driving lights won't turn on. I also noticed that when I use my left blinker, the rear light (in the taillight) will only blink sometimes. Can anyone please help me find the problem, and where to find it? This is my daily driver. I run HID's on relays, so those still work.

Thanks

Break out the wiring diagram and follow the wires. Common problem areas include the switch contacts, the connector that goes into the switch, and corrosion in the fusebox. If you search in the electrical section, you can find many posts by myself and Dave (Zs-ondabrain) describing this circuit.

Once you get the problem fixed, consider swapping out the bulbs in the running lights & turn signals for LED bulbs. Also clean out any corrosion you find in the bulb sockets. If you swap out your 1157 bulbs for LEDs, you will need electronic flashers for your turn signals and hazard lights.

I'm having trouble trying to find a place to start. I've been looking at the wiring diagram in my Chilton's but its hard to follow for me. Links to any posts describing the circuit would be great.

Thanks

where should my voltange sensor wire for my internal gm 3wire alternator go?

right now, my dash map light works, my headlight switch works (they turn on relays for HID ballasts) and my blinkers and hazards work moslty (left rear turn signal does not work when I use left turn signal but works when I use hazards)

Edited June 23, 201113 yr by wilson_wwsc

The Chiltons wiring diagram is generic & therefore not accurate on some points. Look at the links in my signature and download the FSM. I haven't ever done a GM 3 wire alternator conversion, so I don't know which wire is which. I believe there are writeups online, but you'll have to search for them.

I still dont know where to start looking. Im guessing it something in the engine bay. Where does the combo switch get power from? is there any way I can juse feed 12volt power straight to the switch?

Can you explain the diagram for the combo switch? I cant tell what color wires do what. Basically, if I provide 12v to the switch, which wires needs power to power driving lights? My headlight circuit works with the white plastic plug unplugged on the headlight switch.

A long while ago (maybe 6 months) my stock 240z radio, heater/ac fan unit, and console switches(rear window defogger) started acting funny. They would turn on fine after I start the car cold. Then, after about 5-15 minutes of driving, these items would go off. Recently, they are just always off.

Then, a few days ago, my driving/parking lights failed. I flipped the combo switch off and on, and the driving lights came back on. Not sure what happened. Then, yestereday, all of the driving/parking lights failed. Fuse box in the car is OK. I found a fused wire leading into the firewall (its not an oem wire I don't think) with the fuse housing broken. I replaced this, and the lights still did not turn on. I took the column cover off and found my 9pin connector. I put a 12v power source to the green/blue wire and the lights worked using the combo switch. Then, I took the power wire off and started my car, flipped the lights on, and was dazzled/amazed/WTF to see that the lights work. What gives?

they dont work anymore =(

so can i just put a 12volt fused wire straight from the battery/alternator to the green/blue wire on the combo switch? What amperage fuse would I use?

I had similar problems with the headlights. Turned out to be the headlight switch. They are repairable.

But when I connect the green blue to green white wire on the switch, the lights don't come on. If the problem was the switch, then this should have worked because there would be power in the green blue wire, and the bridge to the green white wire would complete the circuit, and the lights would turn on. Where does the combo switch get power from? Physically, where is the wire on the engine side?

I had similar problems with the headlights. Turned out to be the headlight switch. They are repairable.

they dont work anymore =(

so can i just put a 12volt fused wire straight from the battery/alternator to the green/blue wire on the combo switch? What amperage fuse would I use?

While you are frustrated about your situation, please don't take that approach. Hacking into the wiring usually causes more problems than it solves.

Instead, take careful measurements and report back to us, and you should get helpful advice.

Now, let's start.

I'm attaching a picture of the fusebox cover. The parking light fuse is the third one down on the right. That has been a problem area on a lot of Z cars. The circuit will have enough current to overheat the fusebox in that area, but it can be below the threshold to blow the fuse. In my 73, I have seen this fuse glow orange, and I even had a fusebox melt down. If you go back to my original response to your post, you'll see steps I recommend to reduce the possibility of the circuit melting down.

You should probably inspect the fusebox front & back. That involves disconnecting the battery, removing the center console and taking out the fusebox. Look for corrosion on the back side, especially. When you check fuses, remove them from the fusebox and check them with an ohmmeter. I prefer to see a number instead of using the tone to determine whether or not the fuse is good. That's because there could be just enough contact left to allow a tone, but it's higher resistance. I've actually had fuses melt away from the cap and not blow visibly in the middle. Also take the time to clean the contact areas on the fusebox. Emery paper can do wonders. More helpful hints can be found at the Datsun Z Garage.

After you have inspected/cleaned up your fusebox, reinstall it and reconnect the battery. Verify you have 12 VDC to ground on both sides of the fuse. If you don't have 12 VDC on either side, you most likely have issues with your fusebox still. It could also be the White/Red wire that feeds the fuse is the issue, but that is less likely. You'd have to inspect the connectors under the dash to see if that wire is damaged.

If you have 12VDC on both sides of the fuse, start moving downstream. Check the Green/Blue wire going into the combo switch. If you have 12VDC there, with the switch unplugged, check for continuity between the Green/Blue and Green/White wires coming out of the switch when the switch is in position 1 (running lights). By the way, you can get a new headlight switch from RockAuto if you need one. It's more expensive than rebuilding the old one, but I was happy with the one I got for my 74. (They use the same switch.) If you have voltage there, and the switch is good, follow the Green/White wire downstream. (By the way, if your dash lights are on, but your outside lights aren't, that could be a sign of bad sockets or disconnected wires.)

That's enough to keep you busy. Let us know what you find out.