electrical hell,

[cdub42]

im about ready to pull all my hair out. i been trying to fix this issue for a few weeks and getting no where. my tail lights just up and quit. break lights work, turn signals... left hand blinks like its supposed to but the right hand causes all them to blink. and when i turn on the headlights the tail lights dont light up. when i turn off the headlights the fuse explodes. i have checked all the bulbs, ive made sure the sockets where good, near as i can tell the combination switch is good and the turn signal switch is good. ive taken both apart and cleaned them. my headlights work even without the fuse in. im to the point where i am willing to PAY someone to come fix this. i hate electrical.

[ggzilla]

when i turn off the headlights the fuse explodes

That sounds like your Light Switch is bad and shorting inside when moved a certain way. You could test it by disconnecting and test continuity while moving the switch. I think early Z is negative switched headlights, but there is also HOT in the switch (unlike a 510 switch). Should never be any continuity between ground and hot when moving the switch. I had a similar problem when my dimmer switch was slightly loose on the column.

 

 

About the rear lighst, I've seen this happen before: the rear comination lamp (taillight, T/S, brake) is grounded to the body. If the connection gets slightly corroded, the rear lights all go off. Usually only one side.

 

But...

tail lights just up and quit

break lights work

So it's not the common ground, or the brake lights wouldn't work.

[cdub42]

i had the switch apart and tested it. checked fine. the front blinkers work as they should. the rear, the left works as it should but the right blinks all of them.

[I'm BLUE]

Hazard switch ... take it apart and clean it then test/try if possible.

 

Fusebox's dump all the time in these... just a fun fact. The z store or motorsportauto.com sells new circuit fuse box's for $160-$180 ? now. Used 3 of them without fail. They will always get a bit warm though.

[ggzilla]

i had the switch apart and tested it.

Yes, headlights come on. But did you test it thoroughly for shorts when moving switch back to off?

 

Rather than buy a new Fuse Box, if yours isn't partly burnt a cleaning will usually make it work like new for another 5 years.

[I'm BLUE]

Agreed. Now that I recall ... I don't think I've ever dismantled a non-melted/burnt 240z fusebox though lol.

I have had mixed results on fuse-box repairs/soldering/vinegar dipping.

[DanielC]

Wacky electrical problems are almost always bad grounds. Just because some lights in the taillight assembly work, that is no test of the ground of the taillight. It is possible for one light in a taillight assembly to ground through other lights in the taillight assembly, if the normal ground is bad.

Here is a picture of a classic symptom of a ground problem, I had with the brake lights on a 521.

The brake light on this taillight is trying to ground through the reverse light, and each light is only getting about 6 volts, because the brake light is grounding through the reverse light, and they are effectively in series, or "daisy chained".

 

This is how you test the ground. You need a voltmeter, and a piece of wire to go from the taillight assembly to the battery. This is a picture of a 521, to give you an example. I hooked up an extra wire to the taillight frame on this truck, like this. It is the yellow wire, with the red terminal.

This wire goes under the truck, and in true Ratsun fashion, it was not long enough, so it got spliced to a blue wire. The blue wire is in this picture of a voltmeter, going to the red lead on the voltmeter. the black lead is just put in the space in the negative battery terminal clamp.

The voltmeter is measuring the voltage between the taillight frame, at the back of the truck, and the negative battery terminal. Notice it reads 6.135 volts.

 

To fix this problem, I ran an extra wire from the frame of the taillight to the frame of the truck. I did this because on a Datsun 521, the taillights are grounded to the bed of the truck, the bed should be grounded to the frame of the truck, and the frame should be grounded to the battery. Your Z-car has no frame.so the body of the car is the main ground.

 

After adding the extra wire this is the voltage between the taillight frame, and the negative battery post.

The voltage drop is .061 of a volt. That is 6/100 of a volt. This is a very good voltage drop. And this is the two brake lights working normally.

A Z-car should be easier. I do not have one, so I cannot describe exactly the taillights ground, but I can make a pretty good guess. The taillight assembly probably has a wire that goes to the sheet metal of the car, and this wire may be under a screw or bolt that holds the taillight assembly to the car, or it may not.

If any rust or corrosion gets in this wire connection, the ground goes away.

 

The other end of the ground is in the engine wiring. Again this is described from what I know about a Datsun 521, but I think there will be some similarities with your Z-car.

 

The negative battery post connect to the engine by a battery cable, on the cylinder head, under a lifting lug, just to the rear of the fuel pump. On this cable, there is also a smaller wire that goes down to the alternator frame, or case. There is a second ground wire there, that goes to a voltage regulator mount. If your car has had an internal regulated alternator put in, this ground wire that held the voltage regulator must still be there, connected to the body sheet metal of the car.

 

The second problem, the light switch. I do not know if a 240Z uses grounded switching for the headlights, or not.

The light switch has two or possibly more independent switches, or circuits. The headlights, with their own fuse, or fuses. The taillight, and side marker lights, again with a different fuse than the headlights. There may also be a fog light circuit, with a fuse, I do not know. It could be you have a problem with the headlight section of the light switch making contact with the taillight section of the switch, and if the headlights are a ground side switching system, this could create some interesting problems.

[cdub42]

well, my fuel pump went out on my way to work this morning. more electrical hell. i think the easiest way to fix this thing is rip all the wires out and rewire the whole car. the more i look for the problem the more problems i find. 40 years of people splicing things in and then removing them to wire something else in has made this thing a tweekers wet dream. i been looking at a ten circuit generic GM harness. im not happy about the price tho.

[ISPKI]

I kind of have the same issue with my 280z. People kept splicing garbage into everything and I have to clean it up. I already got rid of the entire sound system that was installed in the early 90s. Just wire up the harnesses yourself. Material cost is relatively cheap, all it takes is time and patience. From what I read in the FSM, these seem to have several separate wiring harnesses rather than one large one? Might make it easier to single out problems.