Power goes from the ignition switch through the neutral safety switch to the starter solenoid, which closes and cranks the starter:

This schematic doesn't show wire colors or the plugs, so a red/blue wire comes from ignition switch S to an inline plug (make sure that is good), then through a grommet down to the neutral safety switch, back thru the grommet, through the firewall plug to S on the starter solenoid- all of this on a red/blue wire.

 

Mach 1 ?

"the neutral safety switch" ?? i guess if I follow the wire I will find out. Never seen such a guy?
Thanks.

 

Connect your test light to the RED/BLU wire at the "S" post on the starter solenoid and turn the key to "START".

Does the light come on? If yes, then most likely the starter solenoid has gone "belly up". If no, check to make sure the transmission gear selector is firmly in either "PARK" or "NEUTRAL" and try again. If still no light, check the RED/BLU wires at the 4-pin connector to the Neutral Safety Switch in the engine compartment (see pix below). If connection is secure, use test light to probe RED/BLU wire from ignition switch "S" post. I find an "unbent" paper clip slipped in the back of the ignition switch plug, contacting the terminal end, works pretty well for this. Turn key to "START". If no light, ignition switch is probably FUBAR. If light then trace wiring back from switch to 4-pin connector for a break.

 

Okay Bart Wil do on weekend....... Um "test light" you mean

6/12V Circuit Tester with 5 ft. Lead

Amazing deals on this 6/12V Circuit Tester With 5Ft Lead at Harbor Freight. Quality tools & low prices.

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I think I have one.

 

Hold the key in the start position while moving the shift lever slowly through every position. Sometimes it will start between neutral and reverse or something like that. A bad NSS has even been known to start the car in a drive gear.

 

The "doo-dad" circled in red. The red arrow points to the harness which, on a Mustang, will go the opposite direction up along the tunnel to the firewall.

A voltmeter is MUCH better than a test light. He was just saying to use a test light because it is cheap and you were more likely to have one. Yes put the other probe anywhere you can get a good ground. Since you will be right next to the battery, connect to the battery negative and solenoid terminal S- the small terminal in the front, and have someone turn the key with it in neutral or park. You should get 12v. I should mention not to stand in front of the car when doing this. If the neutral safety switch is not adjusted properly and its in gear you could get run over.
If you don't get 12v, jiggle the shifter around and see if you can get it to work. if no joy, then follow the wire back to the neutral safety switch, then ignition switch. If you do get voltage at solenoid S but it doesn't click/start, then its the solenoid.

Thank You MACH one ...so much

I wrote my reply last night when thinking.....

So this morning , To start I checked my Battery level reading 6.2 amp. I had a float charger on the guy all week. BUt It still drained. This is my gagarge queen which gets little exercise.

I installed my tempo daily driver battery at 12.6 and boom mustang fired right up after some gas !!!

So mystery solved. I hate Batteries!

Thanks Mach One, BART and Cougar ! Now on to more issues on the list !

 

KISS always start from basics.