How do I solve issues with my car's alarm and door lock system?

Here's an easy and inexpensive fix
by Ferman Lao | Oct 9, 2017


Hello Top Gear Philippines!

I have a troubleshooting question I was wondering I could ask you guys. I don't know any car enthusiasts so you're the closest thing I've got. 

A few weeks ago during a trip to Tagaytay, my car doors suddenly decided to stop working with my alarm system. They wouldn't open or close with the alarm or when the engine is killed/started. I had to use the key to lock and unlock my doors separately. The locks still worked centrally though—they just didn't work with the alarm. 

Continue reading below ↓

Today it suddenly started working again 'automagically', like it never happened. Now before I go cry wolf to a car mechanic or electrician, I wanted to ask you if you have any thoughts about what the problem could be. I just want to have some idea and not appear like a total noob (which I am).

Continue reading below ↓
Recommended Videos

Thanks for any insights. (More power! Love your Facebook posts!) 

Daniel Tanpoco


Hi Daniel, 

We're nothing if not car enthusiasts and you're welcome to write in any time for insights!

You don't have much to worry about regarding your concern. It is a fairly common occurrence with an easy and inexpensive fix (most of the time).

The common aftermarket vehicle security system these days typically has a control module which drives its own proprietary door lock actuator. By proprietary, we mean different from OE, as the component itself is a fairly standard part that's used by many aftermarket alarm brands. It works by extending or retracting a linkage as required depending on what the signal it receives from the controller.

Continue reading below ↓

The linkage is usually attached in parallel to the same pushrod that we push or pull on when we manually lock and unlock our doors by another small link (let's call it a connecting tab) that comes with the alarm. The pushrod is what resides inside your door and is what connects the door lock lever/tab, to the lock/unlock mechanism. When the actuator linkage extends or retracts it mimics the motion we impart onto the pushrod when we lock or unlock our doors. 

Now the connecting tab is usually 'clamped' to your pushrod with a set screw. Over time, the set screw may work loose or the tip of it which pushes onto the pushrod may have eroded away. This allows the connecting tab to slide along the pushrod instead of moving the pushrod. Since the mechanical connection between the pushrod and actuator linkage no longer exists, any movement of the linkage isn't transferred to the pushrod. This results in non-functioning door locks when you push your remote to lock or unlock your car door. It's the same reason why your doors do not lock or unlock when you turn your engine on or off.

Continue reading below ↓

Sometimes, for whatever reason, the connecting tab may work temporarily as your own experience shows. I wouldn't worry about it until the doors don't lock anymore with the alarm, but I would make sure to check that the doors do lock until I get them fixed.

In any case, this does not mean your alarm isn't armed when the doors don't work, it just means the actuator malfunctioned and you just lock them manually.

The fix is easy, too. The connecting tab can either be tightened or replaced as needed. Any alarm installer should usually have spare connecting tabs. If they don't they should come with the actuator and you would need to buy the actuator to get them. 

As to why you could still lock them centrally? That's your original equipment (OE) power door lock electronics working. It's independent of the aftermarket security system's and that's the preferred option. In the early days, installers would tap into the OE door lock electronics to get the doors to work in unison with the alarm. Occasionally, an inexperienced installer would tap into the wrong wire to damage the OE electronics. Thankfully, those days are long and gone. 

Continue reading below ↓

Thanks for writing in!


Also Read

  • Quiz Results

  • TGP Rating:

    Starts at ₱

    TGP Rating:
    Starts at ₱