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© 2001 Directed Electronics, Inc. Vista, CA 7
5. Cut the wire you suspect of being the starter wire.
6. Attempt to start the car. If the starter engages, reconnect it and go back to Step 3. If the starter does not
turn over, you have the right 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.
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.
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 steering column. The same wire can often be accessed in the kick panel or running board.
NOTE: Many Toyotas and other Asian vehicles, send a (-) signal from the switch to a relay. The
relay then sends (+)12V to the bulbs. Whenever you have difficulty finding a (+) parking light wire
near the switch, simply test the wires at any switch or control panel that is lit by the instrument
panel lighting. Remember, you need a (+) parking light wire that does not vary with the dimmer
setting.
finding a (+) parking light wire
finding the accessory wire
finding the 12V switched ignition wire