I'm in the process of installing a boost gauge for the Roush supercharger.

I need two positive power points:

1. One which turns on when you put the key in, and stays on while you crank the engine.

2. One which turns on when you put the key in but does not stay on while cranking the engine.

#1 was easy, fuse circuit 1 ( Run/Accessory, Wipers, Instrument Cluster)

#2 is turning out to be difficult because its next to impossible for me to hold a multi-meter to the circuit while turning the ignition key.

I've found a few circuits that stay on all the time (key in or out), such as the overhead power, the console power point and the rear power point, but I need something that turns off when I remove the key.

The reason is the boost gauge zeros out during the crank cycle to calibrate itself, and the gauge uses the power off cycle during crank to do this. This is for a tech article that will go on this site.

 

Hmmm seems to me like fuse 1 would be what you want for #2 and fuse 13, 14, 15, 16, 18, 19, 27 and 25 for #1. I'm going to look at these diagrams closer, the way they have the ignition switch mapped is confusing to say the least.

 

try dk.blue/lt.green at the ignition harness. that should be an ignition wire. should drop out during crank. im sure you know....but test it to be sure.

 

Already tested fuse 1. It stays on during the cranking cycle. About 1-2 volt drop, but only because of the load the starter creates.

 

Hmmm I wonder if there are some variations, it says fuse 1 is windshield wipers as well as some other things, and I know my windshield wipers cut off during cranking. It's a 10 amp right?

 

What year and model truck is it?
I'm with screwy on this.
I looked at the diagrams for a 2004 F150 and fuse 1 is only live in run/accessory position.
Fuses 13,14,15,16,18,19,27,28 are hot in run/start position.

 

I'm with black04lariat on this one....Go under the column and probe this wire, It goes low during the crank cycle.
Rich

 

Its a 2006 F150. I tested the circuit during cranking... I'll double-check but I'm not hopeful.

 

It looks to be the same for a 06.
You can find both of those sources at the ignition switch wiring as was suggested.
Pin 1 dark blue/light green- voltage supplied in run and start.
Pin 6 black/light green- voltage supplied in run and accessory.
If you tap in their put a fuse in them as close to your connection as possible.