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➤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 avail able to
the starter motor.
How to find (+)12V ignition with your multimeter:
Set to DCV or DC voltage (12V or 20V is fine).1.
Attach the (-) probe of the meter to chassis ground.2.
Probe the wire you suspect of being the ignition wire. The steering column 3.
harness or ig ni tion switch harness is an excellent place to find this wire.
Turn the ignition key switch to the run position. If your meter reads (+)12V, 4.
go to the next step. If it does not read (+)12V, probe another wire.
Now turn the key to the start po si tion. The meter display should stay steady, 5.
not drop ping 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 ig ni tion wire.
➤ Accessory wire
An accessory wire will show (+)12V when the key is in the accessory and run
positions. It will not show (+)12V during the cranking cycle. There will often be
more than one accessory wire in the ignition harness. The correct accessory
wire will power the vehicle's climate control system. Some vehicles may have
separate wires for the blower motor and the air conditioning compressor. In
such cases, it will be necessary to add a relay to power the second accessory
wire.
➤ (+) Parking light wire
Most vehicles use a (+) parking light circuit. The (+) parking light wire is often
found near the light switch. In many vehicles the light switch is built into the turn
signal lever; in these vehicles the parking light wire can be found in the steer-
ing column. The same wire can often be accessed in the kick panel or running
board.