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Positive Switched Dome lighting
-8-
CONNECTING THE DOME LIGHTS
The dome lights in the video monitor require three connections to the vehicle's wiring. There are two
common types of dome light circuits used, positive or negative switched. Positive systems supply
voltage to the interior lights to turn them on, negative switched systems apply ground to illuminate the
bulbs. To determine which system you have you must locate the wires at the dome light. On a positive
switched system, with all the doors closed and the lights out, both wires at the dome light will rest at
ground. When the light is activated, one of these wires will switch to +12 vdc. This is the vehicle's
switching wire. On a negative switched system, with all the doors closed and the lights out, both wires at
the dome light will rest at + 12vdc. When the light is activated, one of these wires will switch to ground.
This is the switching wire.
For positive systems, connect the purple / brown (Lamp auto) wire to the vehicle's switched wire. Then
connect the red / black (lamp on) wire to a fused constant 12 volt source and the black / red (lamp
common) wire to a good ground. Positive systems are commonly found on Ford vehicles.
For negative systems, connect the purple / brown (Lamp auto) wire to the vehicle's switched wire. Then
connect the red / black (lamp on) wire to a good ground and the black / red (lamp common) wire to fused
constant 12 volt source. Negative systems are commonly found on General Motors and import vehicles.
Note:
Some vehicles which incorporate transistorized control of the dome light circuit, such as the 1999 Dodge
Caravan, may require that the purple / brown (Lamp auto) wire be connected to the door pin switch wire,
as the additional current draw of the Monitor's lights may not be supported by the output of the vehicles
body control computer.
Red / black - Lamp on
Black / red - Lamp common
Purple / brown - Lamp Auto
To 12 pin
connector
on Monitor
To
constant
+12vdc
To
constant
+12vdc
Factory Door ajar
switch or Body
Control computer
Factory Dome light circuit