Comparing Vehicle Car Locks for DIY Installation Comparing Vehicle Car Locks for DIY Installation

When deciding to install your own car door lock, there are several types available that differ in both their structure and their compatibility with certain vehicle makes and models. It is necessary to do some homework in order to tell the lock types apart and which one is correct for your vehicle. There are a few steps to take when inspecting the switch type of your lock.

What You Will Need:

Multi-meter for determining voltage readings from lock wires


Step 1: Visual Inspection

First determine if there is an external door lock switch on the inside panel of your driver’s side door. If you do not see one, you have a lock system known as a vacuum type. A vacuum type system consists of three wires; the first is the ground wire, the second will always read 12 volts of direct current (DC), and the third will alternate between reading 12 volts and acting as the ground wire.

Step 2: Test Wires

Use your multi-meter to check the DC voltage of each wire that is connected to each of the mechanisms for unlock and lock. Measure each wire for the consistency of the voltage from the ground wires, duration of pulses, and resistance.

Step 3: Compare Measurements to Factory Descriptions

There are six types of lock switches most commonly found on the auto market, with a seventh less common type known as Special or Custom that has additional components or connections. The common six types are known as Single Wire, Three Wire Negative, Three Wire Positive, Four Wire Reversal, Five Wire Alternating, and Vacuum Type. Knowing which of these your vehicle has will determine which lock type you will need to purchase for your DIY installation.

Both Three Wire Negative and Three Wire Positive systems consist of three wires, where one always acts as the ground wire and the other two have alternating voltage, depending on whether lock/unlock is being activated.

Four Wire Reversal systems are structured the same as both Three Wire systems, except for an additional wire that has no reading when it is at rest and reads 12 volts when the unlock switch is activated.  

Five Wire Alternating systems can actually have either five or six wires, with either one or two wires acting as the ground wire and also one or two acting as a constant 12 volt wire. A vacuum type, as described before, is a more simplified switch system and is typically found in older vehicles.

Step 4: Installing Your Lock

It is a good idea to comparison-shop for car door lock kits once you have found the one compatible with your actuator system. Many locks can vary in complexity and cost; be especially wary of vendors that claim installation with take more than removing the interior panel of the driver’s side door. This is never the case unless there is internal damage that needs to be fixed at the same time. Follow the instructions from your installation kit carefully, and be especially cautious not to remove any parts of the original lock rod assembly or to bump them out of place.     

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