Hello everyone I had a question about voltage. I am a newbie when it comes to wiring and electrical but I did my research and read the forums. 
 

I have a 1977 280z and it looks like someone’s been in there trying to figure out the issue. Missing bolts etc. anyways with my multimeter I tested the coil and the resistor and voltage. 
 

the voltage was off.. well there was none with the key on the on position, testing on the first terminal on the resistor. so this is what I checked, I went to the battery and checked the cables those are good, car turns over. I looked at the wiring diagram and found the black and white wire that leads to the ignition relay. That wire read at -12.45 volts. As if I I had my wires crossed on my volt meter. Then I searched and found the red and white wire that leads to the battery. And again same thing that wire read -12.45.. I went back to the battery terminals and tested there and that was +12.45. Sooo my question is why is it reading as negative in the wires? Is this normal? Andy ideas as to why the black and white wire that goes to the resistor is getting no power.. 

The only thing that comes up is your car has the Plus on the chassis.. the battery cables are on the wrong pole? they are different diameters so the cables are on the wrong spot.

Does the Plus go to your chassis? and the minus go's to the starter? 

The ground should be minus and the big plus lead should go to the starter! Pictures show more than words! I would like to see whats the case ..

14 hours ago, 280zdude said:

I went to the battery and checked the cables those are good, car turns over. 

I looked at the wiring diagram and found the black and white wire that leads to the ignition relay. That wire read at -12.45 volts. As if I I had my wires crossed on my volt meter.

If the starter works correctly, and the battery measures correctly, it seems likely that you might be placing your probes in the wrong areas or somebody has reversed some wires.  

Go back to the source of the power to the coil and see what readings you get.

I responded to your other post: 

As I said in the other thread, you are leaving out important context of HOW you are measuring the voltage. Where are you placing the positive and negative probes?

Adding to this thread, what is the voltage from the positive battery terminal to the body? What is the voltage from the negative battery terminal to the body?

I have never heard of anything good happening to a 280Z if the battery terminals are swapped.

Here is an example of checking for voltage at the coil. For your issue, you could put the positive probe at the black/white wire at the ballast resistor. 

 

 

Ok thanks for the reply’s I’ll do everything you guys are saying and try to take pics. and get back to you! 

At the coil there is no voltage. Red prob to the + of coil and black probe to strut tour. 
 

at the ignition switch. I connect the red and white wire to the red probe and the black probe to the body such as the door hinge bolt any bear metal under the car. 
 

Same goes for the black and white on the ignition relay. 

9 hours ago, dutchzcarguy said:

The only thing that comes up is your car has the Plus on the chassis.. the battery cables are on the wrong pole? they are different diameters so the cables are on the wrong spot.

Does the Plus go to your chassis? and the minus go's to the starter? 

The ground should be minus and the big plus lead should go to the starter! Pictures show more than words! I would like to see whats the case ..

 Ok took some photos of the battery and the wires leading to the starter 

@SteveJ here’s a photo of my test. Testing the red and white wire which connects to the ignition switch 

Is your battery connected backward?  I can't tell where the cable goes at the circle I drew (weird how pictures are always fuzzy in the area that matters).  Not sure how the starter can work backward but maybe it can.  It's a DC motor and solenoids are just magnetic coils.  I wonder if your engine is spinning backward.  That would be a new one, never heard of it happening.

The positive cable should be connected to the solenoid, the small cylinder on the starter motor.  The negative cable should be connected to the starter mounting bolt.

 

Edited December 23, 20204 yr by Zed Head

Where does it go?

Your battery cables are probably swapped. Again, the way to confirm is to measure voltage from the positive terminal of the battery to the body and from the negative terminal of the battery to the body. If the battery is connected properly, you should see 12VDC from the positive battery terminal to the body and zero from the negative battery terminal to the body. 

Nothing good ever comes from crossing the streams...

 

Edited December 23, 20204 yr by SteveJ

15 minutes ago, Zed Head said:

Where does it go?

 

Yep, your battery cables are backward.  Hopefully nothing has been damaged.  

The cable that your finger is pointing to should connect to the - post on the battery.  Negative.  Ignore any cable or wire colors around the battery.  Red and black are meaningless.