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Door Locks
Determining Switch Types
Multiple Wire Systems
Single Wire Sytems
Special Systems
Determining Switch Types
To determine what type of door lock switch you are working with,
follow these three steps:
- Locate the harness plugged directly into the back of the door lock switch.
- If there are no external door lock switches, you will most likely have a vacumm type system or an *aftermarket
door lock system with relays, or have an added actuator
that needs relays.
- Next, with your multi meter, probe each of the leads in this harness and write down
the readings during lock, unlock, and at rest positions of the switch. Be sure to
measure for continuity to ground as well as positive DC voltage and pay close
attention to any changes in voltage, resistance, and the duration of pulses.
If the switch is illuminated when the lights are turned on, find this lead(s) first and ignore it.
- Now compare your readings to those listed below.
Single Wire Sytems ( diagrams )
There may be one, two, or three wires in the harness not counting the
illumination wire(s), if any, and only changes in voltage and /or resistance
on one lead to lock and unlock.
Some of these will open a circuit to lock and ground a
lead to unlock. Others will show a difference in resistance to ground or
positive 12 VDC during lock or unlock or both. Vacuum type locks will
change polarity on a single lead to lock and unlock.
3 Wire Negative ( diagram )
There are three wires in the harness not counting the illumination
wire(s), if any. One wire has continuity to ground at all times. Another
wire only shows continuity to ground during lock and (+) 12 VDC at rest.
The last wire only shows continuity to ground during unlock and
(+) 12 VDC at rest.
3 Wire Positive ( diagram )
There are three wires in the harness not counting the illumination
wire(s), if any. One wire has constant (+) 12 VDC at all times. Another
wire only shows (+) 12 VDC during lock and ground at rest. The last
wire only shows (+) 12 VDC during unlock and ground at rest.
4 Wire Reversal ( diagram )
There are four wires in the harness not counting the illumination
wire(s), if any. One wire has constant (+) 12 VDC at all times.
Another wire has continuity to ground at all times. A third wire reads
nothing at rest, and (+) 12VDC during lock and continuity to ground
during unlock. The fourth wire reads nothing at rest, and ground during
lock and (+) 12VDC during unlock.
5 Wire Alternating (+) 12 VDC ( diagram )
There are four, five, or six wires in the harness not counting the
illumination wire(s), if any. One or two of the wires has constant
(+) 12 VDC at all times. One or two of the wires has continuity to
ground at all times. Another wire reads continuity to ground at rest,
and (+) 12VDC during lock. The last wire reads continuity to ground
at rest, and (+) 12VDC during unlock.
Vacumm Type ( diagram )
There is no external switch (switch is contained in the drivers
door lock actuator) or it has three wires not counting the illumination
wire(s), if any. One wire always shows continuity to ground. Another
always shows constant (+) 12 VDC. The third wire changes, reading
continuity to ground or (+) 12 VDC depending on the position of the
door locks.
Added Actuator ( s ) ( diagram )
The two leads of the actuator(s) will normally rest at ground,
if wired as shown in this diagram,
but may rest at (+) 12 VDC. Polarity changes on one lead during
lock and on the other lead during unlock.
*If you are dealing with an
aftermarket door lock system,
locate and measure each coil lead of the lock and unlock relays.
Then connect to the leads that activate each relay accordingly.
If the system has a relay module, it may also have
two leads (pig tail) that will energize the coils of the internal relays. These will
usually be negative inputs. Some will have both positive and negative
inputs to work with any alarm or keyless entry without the need for
additional relays.
Special ( diagrams )
These applications will be similiar to others, but will require
additional connections, parts, or both.
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