Finding The Wait-To-Start Bulb Wire For Diesels; Finding A (+) Parking Light Wire - Viper 7900 Installation Manual

transmission computers.
IMPORTANT! Do not test tachometer wires using a test light or logic probe (computer safe test light)! This will
damage the vehicle.
How to find a tachometer wire with your multimeter:
1. Set to ACV or AC voltage (12V or 20V is fine).
2. Attach the (-) probe of the meter to chassis ground.
3. Start and run the vehicle.
4. Probe the wire you suspect of being the tachometer wire with the red probe of the meter.
5. If this is the correct wire the meter will read between 1V and 6V.

finding the wait-to-start bulb wire for diesels

In diesel vehicles it is necessary to interface with the wire that turns on the WAIT TO START light in the
dashboard. This wire illuminates the bulb until the vehicle's glow plugs are properly heated. When the light
goes out the vehicle can be started. This wire is always available at the connector leading to the bulb in
the dashboard. It can also be found at the Engine Control Module (ECM) in many vehicles.
To test and determine the polarity of this wire:
1. Set your multimeter to DCV or DC voltage (12 or 20V is fine).
2. Attach the (+) probe of the meter to (+)12V.
3. Probe the wire that you suspect leads to the bulb with the (-) probe of the meter.
4. Turn the ignition switch to the ON position.
5. If the meter indicates 12 volts until the light goes out you have isolated the correct wire and the wire's
polarity is negative (ground while the bulb is on).
6. If the meter reads zero volts until the light goes out and then reads 12 volts, you have isolated the
correct wire and the wire's polarity is positive.

finding a (+) parking light wire

The (+) parking light wire is often found near the switch. Many cars have the switch built into the turn
signal lever, and in these cars the parking light wire can be found in the steering column. The same wire is
often available in the kick panel or running board.
NOTE: Many Toyotas, as well as many 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 which is lit by the instrument panel lighting.
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