Truck Repair: 89 Ford 7.3 No Start, ford club wagon, starter selenoid

Question
Where is the netural safety switch located at on an automatic? I was able to start by turning the ignition on and jumping the starter selenoid under the hood which i just replaced. I then checked the ignition wire going to the starter selenoid when in the start position, and i am not getting any voltage to the selenoid from the ignition.
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Followup To

Question -
I recientlt bought a 1989 Ford Club Wagon with the 7.3L Diesel in it, started and ran fine when i picked it up. Now all it does is click (sound comes from the back of the engine with the dog house off) sparaticly when you turn it on. If i turnit to the start position it does absolutly onthing, no starter click or any thing!

Answer -
well the sound you are hearing when you turn it on might be the glow plugs... what i would check is the "n" safety switch. try putting it in netral and then start if its a auto. if manual check the clutch switch and "n" safety switch on the side of trans if equi. clutch safety switch sould be under dash above clucth ped. thanks and let me know how that goes

Answer
on the driver side of the trans there should be a plug going into the trans with 2 wires if you were to jump these wires together and it starts by the key, switch is bad and it should twist out of the trans with a wrench.. let me know how that goes .thanks for the ?