Neutral safety switch

Help Support 7173Mustangs.com:

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Hey guys it’s been a while since I’ve posted. My Mustang project was put on hold for a few years and I just finally got started back on it. The good news is I got the engine running and boy it runs great. I’m having problems cranking the engine from the key switch. I can start the car by jumping the solenoid.  I have a 460 with a C6 transmission.  Have installed a new ignition switch, starter solenoid and cleaned the key cylinder.  The previous owner had a manual transmission but I installed an automatic.  Is there anyway I can bypass the safety neutral switch just to verify this is the problem? Once I know this is the problem then I will figure out how to install a working neutral safety switch.  There are several wires on the driver side apron that seems to go nowhere. I believe one of these may be for the neutral safety switch. Any help would be greatly appreciated.

 

midlife

Shorts checker
Joined
Jan 24, 2012
Messages
4,076
Reaction score
490
Location
Tucson, AZ
My Car
No Mustangs at the moment.
NSS wires are red/blue. There should be a 4 pin square plug on the headlight harness that mates with the NSS/Backup Light harness. Simply jumper the two red/blue wires to bypass the NSS. Be careful that the car is NOT in gear.

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
NSS wires are red/blue.  There should be a 4 pin square plug on the headlight harness that mates with the NSS/Backup Light harness.  Simply jumper the two red/blue wires to bypass the NSS.  Be careful that the car is NOT in gear.
I just tried that and still nothing. When I turn my key in the on position I don’t even hear the electric fuel pump running. The way I wired my solenoid is the big yellow wire and battery cable goes to the left (front) big post on the solenoid and the rear big post to the starter wire. The red with green stripe goes to the i terminal and my fuel pump relay wire and the red with blue stripe wire goes to the s terminal. I have a one wire alternator going to the battery.

 

midlife

Shorts checker
Joined
Jan 24, 2012
Messages
4,076
Reaction score
490
Location
Tucson, AZ
My Car
No Mustangs at the moment.
Time to isolate where the problem is. Disconnect the NSS/BU plug and probe the red/blue wires from the headlight harness: one of them should be 12V when the key is in CRANK position. If neither one is, you may have a bad ignition switch or faulty wiring somewhere.

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Time to isolate where the problem is.  Disconnect the NSS/BU plug and probe the red/blue wires from the headlight harness: one of them should be 12V when the key is in CRANK position.  If neither one is, you may have a bad ignition switch or faulty wiring
I checked and one of the red wires with blue stripes will light up only in the crank position. I hope this is a good thing.

 
Last edited by a moderator:

Don C

Fords Forever
Joined
Jan 1, 2012
Messages
8,107
Reaction score
862
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
The only time the red/light blue wire that is connected to the "S" terminal, and the only time the "S" terminal, have voltage is when the ignition is in start position. This means the only time your fuel pump will run is when you are trying to start the car.

Yes, that is a good thing, only one of the red/light blue wires should have voltage with the ignition in the start position, when the connector is not connected. That is the side that comes from the ignition switch, the other one goes to the"S" terminal on the solenoid. Jump those two wires together and see if you have start voltage at the "S" terminal.

 
Joined
Jan 7, 2015
Messages
8,032
Reaction score
489
Location
Western North Carolina
My Car
Multiple Mustangs!
I would almost bet your ignition switch is out of position. When you turn the key there is a rod that goes down the steering column and links to the ignition switch. There are two bolts holding it to the column. Loosen the bolts and slide the switch toward the steering wheel. See if that works.

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
The only time the red/light blue wire that is connected to the "S" terminal, and the only time the "S" terminal, have voltage is when the ignition is in start position. This means the only time your fuel pump will run is when you are trying to start the car.

Yes, that is a good thing, only one of the red/light blue wires should have voltage with the ignition in the start position, when the connector is not connected. That is the side that comes from the ignition switch, the other one goes to the"S" terminal on the solenoid. Jump those two wires together and see if you have start voltage at the "S" terminal.
Thank you, thank you, thank you! I tapped into the wire and now I can start the car using the key. Now I just need to figure out how to incorporate a NSS to the C6 transmission ?

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
I would almost bet your ignition switch is out of position. When you turn the key there is a rod that goes down the steering column and links to the ignition switch. There are two bolts holding it to the column. Loosen the bolts and slide the switch toward the steering wheel. See if that works.
I thought that too so I dropped the steering column and disconnected the rod then manually controlled the ignition switch by hand just to be absolutely sure.

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
The NSS mounts on the shift linkage on the side of the transmission. This thread and other links in it should help

https://www.7173mustangs.com/thread-neutral-safety-switch--32140
Another problem arose. The car started fine from the key cylinder but when I went to turn it off the car kept running...with the ignition off and the keys out. I disconnected the battery and it continued to run. I finally had to disconnect the main lead to the distributor. I know there has to be some wiring wrong on the solenoid. I have the big yellow wire hooked up to the battery side of the ignition coil. Is this correct?

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Another problem arose. The car started fine from the key cylinder but when I went to turn it off the car kept running...with the ignition off and the keys out. I disconnected the battery and it continued to run. I finally had to disconnect the main lead to the distributor. I know there has to be some wiring wrong on the solenoid. I have the big yellow wire hooked up to the battery side of the ignition

 

Don C

Fords Forever
Joined
Jan 1, 2012
Messages
8,107
Reaction score
862
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
The wire that connects to the positive side of the coil and comes from the ignition switch is red with a light green stripe, and runs through the ballast (resistor) wire. As you learned, you cannot run the ignition coil directly from the battery, as long as the engine runs the alternator produces electricity, the alternator connects directly to that yellow wire.

If you have points, whenever the engine is not running and the points are closed, the coil will constantly be energized, quickly discharging the battery and overheating the coil. If you have an aftermarket electronic ignition you risk damaging it, also.

If you're going to do work an your car and do your own wiring you're going to have to learn how to wire a car and read wiring diagrams. You're going to need the shop manuals for your car. You can download the wiring diagram for your car under the Mustang Data tab at the upper right of this page.

You can get a wiring tutorial here

https://www.7173mustangs.com/thread-how-to-read-wiring-diagrams?pid=336055#pid336055

 
Last edited by a moderator:

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Thank you Don, you’ve been very helpful. I will try and study the tutorial. Somebody on another post said the starter solenoid using HEI distributor should be wired like this which is the way I wired mine.

Big solid yellow wire - front stud of starter solenoid, along with BATT (+) cable

Light green red stripe - radio condensor (leave disconnected if you don't have one)

Red with green stripe - "I" terminal of starter solenoid

Red with light blue stripe- "S" terminal of starter soleoid

White with black stripe - Alternator "STA" terminal to "S" on the regulator connector

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Sorry, I meant the big yellow wire from the factory harness (has a fusible link) is connected to the battery side of the solenoid. I have the wire coming from the distributor connected to the S terminal of the solenoid. Sorry, I’m horrible with wiring.

 

Don C

Fords Forever
Joined
Jan 1, 2012
Messages
8,107
Reaction score
862
Location
Springfield, OR
My Car
1971 Mustang Sportroof M code
The S terminal on the starter solenoid only has 12 volts applied to it when the ignition switch is in the start position. The solenoid is an electrically activated heavy duty switch that then connects the battery to the starter. It is a momentary switch that disengages as soon as the ignition switch is released from the start position and the S terminal no longer has 12 volts on it.

The S terminal will not supply 12 volts to your ignition coil. It has zero volts until the ignition switch is turned to start.

For a stock 12 volt ignition system the voltage to the coil is reduced to approximately 8 volts by a ballast resistor, which for our cars is a short section of resistor wire between the ignition switch and the ignition coil. The purpose of this voltage reduction is to reduce sparking of the ignition points when they open and close. This sparking causes the contacts to erode, and the lower voltage greatly extends the life of the points.

Some aftermarket electronic distributors,or distributer modules, require 12 volts for both the distributor and coil, some for just the distributor and leave the coil at the reduced voltage, others run on reduced voltage.

 
Last edited by a moderator:

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Well I went out this morning thinking the ignition switch was faulty and replaced it with a known good one. It started just fine but when I tried to shut the car off it continued to run with the key out. Here’s a few pictures of my solenoid, distributor and where I spliced into the red with blue striped wire. Here’s what’s hooked up to the solenoid. I was able to move my fuel pump wire and connect it to the white with black striped wire since it had power only in the run position. I have my single wire alternator wire connected to the battery.

Big solid yellow wire - front stud of starter solenoid, along with BATT (+) cable

Light green red stripe - radio condensor (leave disconnected if you don't have one)

Red with green stripe - "I" terminal of starter solenoid

Red with light blue stripe- "S" terminal of starter soleoid

White with black stripe - Alternator "STA" terminal to "S" on the regulator connector







image upload

 

Robnbama

Well-known member
Joined
May 8, 2012
Messages
51
Reaction score
0
Location
Attalla, Alabama
My Car
1973 Ford Mustang Mach one
Finally figured it out. Thanks for all the advice. I couldn’t have done it without you!

 
Top