Finding The Starter Wire; Finding The Accessory Wire; Finding The Tachometer Wire - Viper 771XV Installation Manual

f f i i n n d d i i n n g g t t h h e e s s t t a a r r t t e e r r w w i i r r e e
The starter wire provides 12V directly to the starter or to a relay controlling the 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.
H H o o w w t t o o f f i i n n d d t t h h e e s s t t a a r r t t e e r r w w i i r r e e w w i i t t h h y y o o u u r r m m u u l l t t i i m m e e t t e e r r : :
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 starter wire. The steering
column is an excellent place to find this wire. Remember you do not
need to interrupt the starter at the same point you test it. Hiding
your optional starter kill relay and connections is always recommended.
4. Turn the ignition key switch to the start position. Make sure the car
is not in gear! If your meter reads (+)12V, go to the next step. If it doesn't, probe another wire.
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.
f f i i n n d d i i n n g g t t h h e e a a c c c c e e s s s s o o r r y y w w i i r r e e
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.
f f i i n n d d i i n n g g t t h h e e t t a a c c h h o o m m e e t t e e r r w w i i r r e e
To test for a tachometer wire, a multimeter capable of testing AC voltage must be used. The tachometer wire will
show between 1V and 6V AC. In multi-coil ignition systems, the system can learn individual coil wires. Individual
coil wires in a multi-coil ignition system will register lower amounts of AC voltage. Also, if necessary, the system
can use a fuel injector control wire for engine speed sensing. Common locations for a tachometer wire are the
ignition coil itself, the back of the gauges, engine computers, and automatic transmission computers.
I I M M P P O O R R T T A A N N T T ! ! Do not test tachometer wires using a test light or logic probe (computer safe test light)!
This will damage the vehicle.
H H o o w w t t o o f f i i n n d d a a t t a a c c h h o o m m e e t t e e r r w w i i r r e e w w i i t t h h y y o o u u r r m m u u l l t t i i m m e e t t e e r r : :
1. Set to ACV or AC voltage (12V or 20V is fine).
2. Attach the (-) probe of the meter to chassis ground.
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