Type H: Negative (-) Multiplex - Directed Electronics Python 1500 esp Installation Manual

type H: negative (-) multiplex

The system is most commonly found in Ford, Mazda, Chrysler and GM vehicles. The door lock switch or door key
cylinder may contain either one or two resistors.
single-resistor type
If one resistor is used in the door lock switch/key cylinder, the wire will pulse ground in one direction and resist-
ance to ground when operated in the opposite direction.
two-resistor type
If two resistors are used in the factory door lock switch/key cylinder, the door lock switch/key cylinder will read
resistance to ground in both directions.
determining the proper resistor values
To determine the resistor values, the door lock switch/key cylinder must be isolated from the factory door lock
system. For all testing, use a calibrated digital multimeter that is set to ohms.
1. Cut the output wire from the door lock switch/key cylinder in half.
2. Test with the meter from the switch side of the cut door lock switch/key cylinder wire to a reliable ground
source. Some good ground references are the ground input source to the door lock switch/key cylinder or the
battery ground.
3. Operate the door lock switch/key cylinder in both directions to determine the resistor values. If the multi-
meter displays zero resistance in one direction, no resistor is needed for that direction.
4. Once the resistor value(s) is determined, refer to the wiring diagram for proper wiring.
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