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© 2002 Directed Electronics, Inc. Vista, CA
We recommend two possible sources for 12V constant: the (+) terminal of the battery, or the constant supply to
the ignition switch. Always install a fuse within 12 inches of this connection. If the fuse also will be powering
other circuits, such as door locks, a power window module, a Nite-Lite
®
headlight control system, etc., fuse
accordingly.
IMPORTANT!
Do not remove the fuse holder on the red wire. It ensures that the control module has its
own fuse, of the proper value, regardless of how many accessories are added to the main power feed.
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, on the other hand, 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:
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 doesn’t, 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 12V switched ignition wire
obtaining constant 12V