I have a 76 corvette. automatic. Can any one here tell me about this wire. It is the hot pink wire that supplies the current to the neutral safety switch. It is only hot in the switch start position. At times I only have 9.0 volts. I'm thinking that this wire gets hot and a circuit breaker over heats some where.

 

On this schematic when you turn the key to START, 12 volts is sent from the ignition switch on a purple / white wire to the neutral start switch.
The wire comes out of the NSS on a purple wire and ends up at the 'S' terminal on the starter solenoid.

Where is your pink wire located?

http://www.vetteprojects.com/bmv/mis...tte%201976.pdf

 

It is located on the front part of the neutral switch.The wire next to it.is the one ,that goes to the starter. Some where this wire gets it power.

 

That pink wire may be the back-up light lead. Safety start wires are purple-if I remember correctly.

 

The neutral Safety Switch has three sets of contacts.
#1 With the shifter in PARK or NEUTRAL the purple white brings 12 volts to the NSS and out on the purple.

#2 With the shifter in REVERSE, the PINK brings 12 volts in and the GREEN sends 12 volts to the backup lights.

#3 With the shifter in DRIVE or 2 or 1, the pink brings 12 volts in and out on the pink white to power up the SEAT BELT light and buzzer.



You should have 12 volts or battery voltage on all the inputs.

Check the NSS switch for resistance and check both sides of the STOP-HAZ fuse.

 

In the front the wires or purple and a purple with white strip. this wire is the one that has only 9 volts at times.

the back has two wires one pink and one green theses are back up lights.

where does the purple and white wire gets it power from the other purple wire I think goes to the starter it has the same volts as the purple white in the start position

my switch does not look like the one above

 

OK, your switch does not have the pink white so it must look like this one.

https://willcoxcorvette.com/corvette...utomatic-76-82

Is the starter turning over when you test the purple?
If yes then the solenoid and starter are causing the voltage drop.

 

When there is 9 volts,there is no start. At the first start in the morning,there are 12 volts.The car starts up fine. after about thirty minutes with electric fans on and the engine hot. Cut it off and some times it won't start there are only 9 volts .There are 12 at the alternator and starter. If you let it sit for about two hours, check the voltage and there are 12. turn the key it starts.There has got to be a circult that is over heating and needs to be replaced

 

You have the typical hot starter no-start issue that plagued GM cars for 30+ years until they got smart and started fixing it with permanent magnet starters and/or relays in the solenoid circuit.

Basically, you have a poor connection somewhere between the battery and the solenoid S terminal. Without getting too technical, the solenoid draws a LOT of current when first energized until the starter engages. Then, when hot it requires the higher current plus more voltage which causes a marginal circuit to fail. The solenoid then fails to energize and the high current causes the voltage drop that you see.

Go to the fuse block and check the voltage at the "BAT" terminal when you try to start while it's hot.

If it also drops down then start examining the bulkhead connector and the wiring between the bulkhead connector and the large battery post on the solenoid.

If the voltage doesn't drop then examine the wiring between the fuse block to the ignition switch then to the neutral safety switch.

The most likely cause is a poor connection or a damaged fusible link. A poor connection would likely should show signs of heat damage.

 

Where is the bat terminal on the fuse block? The large post on the starter always have 12 volts

 

Any fuse or terminal that has constant 12V power will work as the bat terminal.

 

You are in good hands with Lionelhutz.
Here's a typical fuse box:


All I can add is to check the condition of the battery and that the cables and connections are good, and don't forget the starter to frame connection.

 

I have parts every where.
The fuse box has 12 volts at the ignition terminal..there are 12 volts coming into the ignition switch, the purple and white wire has 12 volt in the start position at the ignition switch. once it arrives at the neutral switch there is only 9 volts. Once this wire leaves the ignition switch does it connect to any thing before it arrives at the neutral switch. Can I just replace this wire with a new one?

Thanks

 

On the above schematic, it goes through the bulkhead connector at #9.
Before you open that up, what is the voltage at the end of the purple white with it disconnected from the NSS and what is the resistance in and out of the NSS?

 

This is what I did .I disconnected the purple-white wire from the ignition switch. from the battery I connected a hot wire with 12 volts.to this end.I disconnected the same purple-white wire from the nss. there was only 9 volts.
After the wire leaves the ignition switch is there any thing else hooked to it. If it is a straight wire this should not happen. unless there is a circult breaker build in the wire and it is bad. Your thoughts on this

 

The root cause of your voltage drop is in the bulkhead connection.
You can open it up and clean the corrosion and be done with the problem.
Alternate fix. Yes, you can run a new separate wire purple white wire.
The P/W does not branch off to anything else and there is no separate fuse or circuit breaker on that line.

 

you are right about the wire. I traced it today, from the nss to the ignition switch. no burnt spots or cuts .I took the top of the dash off. In checking the bulk head I'm I looking for the power wire coming from the battery, or just a bad connection?

 

The purple/white wire does not go through the bulkhead connector.

I'm still not clear on your troubleshooting. You disconnected both ends of the purple/white wire, applied 12V to one end with a jumper wire and the measured 9V at the other unconnected end?


The above voltages were all measured trying to start the engine when it would not crank, correct?

 

Am I not reading the schematic correctly?

 

The purple/white goes from the ignition switch to the NSS.

The purple you put an arrow to goes from the NSS through the bulkhead connected to the starter motor solenoid.