No Crank Wiring Issue

Greetings from Reno, Nevada,

I have a wiring issue that I was hoping to get some help to correct... I have a 69 Mustang Fastback with a 429/460 engine and a Gearstar built Ford AOD transmission. My issue is that I replaced the complete dash wiring with a new harness (purchased from CJ Pony Parts p/n WUD13) and now I can not get the car to crank over. Everything else (electrical) works on the car - Headlights, brake lights, taillights, turn signals, dash lights , etc. But the car will not crank over.
- There is no crank voltage at the "S" terminal (Blue/Red wire) on the starter relay.
- There is 12V of power at the ignition switch "S" terminal (Blue/Red wire) when the key is put in start (crank) mode.
- With the key in the "on" position I checked all the fuses in the new fuse box and they all light up except the small 4amp fuse - the fuse is good but I just don't get any voltage.
- When I input a test light probe into the Blue/Red wire coming off the ignition switch and the clip is put to ground the car will start up.
- The 4amp fuse location is also a Blue/Red wire and I took the fuse box off the firewall location and checked all the wire pins and everything looks okay.
- Voltage is getting to the transmission harness (automatic trans) for the neutral safety switch and the neutral safety switch is brand new.
- I also replaced the ignition switch just in case the old one was going bad.

My electrical skills are limited so I do not understand why the car will start up if I stick a test light probe into the Blue/Red wire... I double checked my dash harness for any missing ground wires that were not attached but could not find any missing grounds. I also made sure that any ground wires were attached to clean metal contact.
The car did start up fine with the old harness so I must have screwed something up with the new wiring...

Any ideas or suggestions would be greatly appreciated.
 
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You might have the start wire on the wrong terminal of the ignition switch, ive done that a few times. If its on the right spot, try holding the key in the crank position while jiggling the shifter in park or neutral. Worst case scenario, rewire the circuit.

shem
 
You might have the start wire on the wrong terminal of the ignition switch, ive done that a few times. If its on the right spot, try holding the key in the crank position while jiggling the shifter in park or neutral. Worst case scenario, rewire the circuit.

shem
Thanks for the reply - much appreciated. I found my issues over the weekend (1) one of the wiring “pins” that goes into the fuse box from the engine compartment through the firewall was not entirely inserted so no connection was not being made (2) this is totally my fault on this one - when I was checking the ignition switch I had pulled it out from the dash and left the switch out of the dash location for continued testing not realizing that I needed to have the ignition switch installed in it’s correct spot in the dash to obtain proper grounding. I learned a lesson in that issue.

Wanted to post my experience in case anyone else runs into that issue.