Finding The 12V Switched Ignition Wire; Finding The Starter Wire - Directed Electronics 591XV Installation Manual

finding the 12V switched ignition wire

The ignition wire is powered when the key is in the run or start position. This is because the ignition wire powers
the ignition system (spark plugs, coil) as well as the fuel delivery system (fuel pump, fuel injection computer).
Accessory wires lose power when the key is in the start position to make more current available to the starter motor.
How to find (+)12V ignition with your multimeter:
1. Set to DCV or DC voltage (12V or 20V is fine).
2. Attach the (-) probe of the meter to chassis ground.
3. Probe the wire you suspect of being the ignition wire. The steering
column harness or ignition switch harness is an excellent place to find
this wire.
4. Turn the ignition key switch to the run position. If your meter reads
(+)12V, go to the next step. If it does not read (+)12V, probe another wire.
5. Now turn the key to the start position. The meter display should stay steady, not dropping by more than a
few tenths of a volt. If it drops close to or all the way to zero, go back to Step 3. If it stays steady at (+)12V,
you have found an ignition wire.

finding the starter wire

The starter wire provides 12V directly to the starter or to a relay controlling starter. In some vehicles, it is
necessary to power a cold start circuit. A cold start circuit will test exactly like a starter circuit, but it does not
control the starter. Instead, the cold start circuit is used to prime the fuel injection system for starting when the
vehicle is cold.
© 2003 Directed Electronics, Inc. Vista, CA
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