Car Alarm Problems: 8 Most-Common Issues & Solutions

Some of the most common problems with alarms are false detections and constantly sounding an alarm at random times.

Car alarms are meant to protect your car from thieves. They monitor the doors being opened, impacts on the outside surface, and should notify you with sound and lights if they detect a problem.

We’ll cover the most common issues with car alarms and how to fix each one, so you don’t have to worry about yours going crazy.

#1 – Your Car Battery Is Dead Or Has A Low Charge

Your car battery provides power to start your car, and it also provides power for the alarm system when the vehicle is parked and locked.

If your alarm continually goes off, no matter if it’s day or night, the battery may have a low charge or be close to completely drained. The alarm may be signaling a problem, but it’s not what you think it is.

How to Fix It

Your battery being drained could be the battery going bad or something drawing significant power while the car is turned off.

A bad battery could have one or more internal power cells that have stopped holding a charge. A normal battery voltage should be around 12.0 volts while the car is turned off and no significant power being drained.

If the battery has one bad cell, it may only hold around 10.0 volts and not have enough charge to start your car. You can have the battery tested and replaced if it is found to be faulty.

A good battery can still be low or dead in the morning if there is a significant power draw while the car is turned off.

Aftermarket accessories like a stereo amplifier that is wired to be always turned on can draw enough power overnight to drain a battery.

An alternator with a bad regulator can also drain a battery overnight. You can use a multimeter to monitor the battery voltage when the car is turned off. By monitoring the voltage or power draw on the battery you can remove fuses to significant circuits in the car to find which circuit is drawing the power from the battery.

You can also test an alternator by starting the car and monitoring the voltage change at the battery terminals. A battery should show 13.6 – 14.6 volts at the battery terminals when the car is running. If it doesn’t, the alternator should be replaced.

#2 – Your Impact Or Movement Sensors Are Set Too Sensitive

Most car alarm systems have motion detection or impact sensors that sound the alarm when something impacts the car or shakes the car.

If they are set too sensitive, they can trigger the alarm at the slightest movement like a bird landing on the hood. Not only is it annoying to have the car alarm constantly sounding for a false trigger, but it can also eventually drain the car battery.

How to Fix It

Aftermarket alarms with shock sensors can be adjusted for sensitivity. You can also move the placement of the sensors to reduce their responsiveness and sensitivity. Most aftermarket alarms have an adjustment dial that needs a small flat-blade screwdriver to turn.

If your alarm system was included by the manufacturer, the sensitivity may be adjustable through a diagnostic scanner. Some car manufacturers are known for troublesome alarm systems that are too sensitive, and many owners prefer to have the alarm sensors turned down to prevent false triggers.

#3 – Your Hood Latch Sensor Is Problematic

Most alarm systems incorporate a hood latch sensor that detects when the hood is opened.

Most are a simple switch that makes an electrical connection when the hood is lifted. These can become problematic over time and often trigger the alarm too easily or sometimes do not trigger it at all.

How to Fix It

Most hood latch sensors make an electrical connection when the sensor actuator extends due to the hood being opened. Some alarm systems have the hood sensor make a ground connection through the body of the sensor and use that to trigger the alarm.

These sensors connected to the body of the car can corrode over time and lose the ability to contact the metal of the car. When that happens, they no longer provide the ground to the alarm and the system may frequently go off or not trigger at all.

These sensors need to be cleaned of dirt and grime to prevent corrosion and they should be sprayed with a protection spray to prevent corrosion from coming back.

#4 – Your Door Lock Sensor Is Faulty

The hood latch sensor protects what is under the hood, while the door lock sensors protect what is in the passenger cabin and trunk areas.

Some alarm models monitor the dome lamp circuit for an electrical connection, while others monitor the lock mechanism. In either case, the alarm should trigger if the door is opened.

How to Fix It

Finding a troublesome door lock circuit can be difficult. Most aftermarket alarms that monitor the dome lamp circuit are connected to the alarm system under the dashboard.

Factory alarm systems may monitor each door lock mechanism and have an electrical connection under the dashboard. To find the cause of a problem, you need to find the connection point and monitor it with a multimeter.

The multimeter will show a change in voltage, or a ground connection being made when the dome lamp circuit transmits power or the lock mechanism in each door transmits a connection.

#5 – Your Key Fob Keeps Triggering The Alarm

The key fob that unlocks and locks the doors can also turn the alarm system on and off at the same time. A faulty key fob can continuously trigger the alarm which can drive you nuts and drain your car battery.

How to Fix It

The key fob can trigger the alarm frequently if the battery is low or the buttons are stuck. The battery can be replaced easily by opening the key fob case and removing the battery.

Most use a small round watch-sized battery that can be purchased at a local store. Some factory alarms may require reprogramming if the battery is replaced in the key fob, and that may require a trip to the dealer.

If the key fob batteries are stuck, they can be cleaned with soap and water. Most key fobs are water-resistant, and you can wipe away dirt and grime. You can also use a cotton swab to get into the hard-to-reach areas to restore the smooth button functions.

#6 – The Alarm Was Installed Incorrectly

Most factory alarms don’t have an installation issue because they are thoroughly tested before being delivered to the customer. Aftermarket alarms though, can always have an installation issue.

How to Fix It

A bad installation can create an immense number of problems and can also affect other electrical systems in the car. Problems such as the alarm continuously being triggered or not triggering correctly can just be the tip of the iceberg.

If you find the alarm doesn’t operate correctly for certain features, you need to have each circuit checked in the installation. The alarm may also have selections to turn functions on and off, and those features can be adjusted by reviewing the owner’s manual that comes with the alarm.

#7 – The Alarm Control Module Has Gone Bad

Every alarm system has a central module that controls the functions of the alarms. Manufacturer alarm systems are integrated into the car’s electrical system and typically don’t go bad without causing other electrical problems.

Aftermarket alarms have separate modules that can go bad over time. When they stop working, the alarm no longer functions correctly.

How to Fix It

Alarm modules usually work for years before they go bad. When they stop working, the electrical board inside the module typically corrodes the connections or an electrical component burns out. Y

ou may be able to have the corrosion removed to restore the alarm functions for an easy fix. Burned components may require taking the module to an electrical service shop that can unsolder the burned component and replace it.

The difficult decision may be to replace the whole alarm system. Modules frequently change from the manufacturer and rarely do they manufacture them to make the module easily replaceable with a newer model.

You may need to have a service center remove the current alarm system and replace it with a new system.

#8 – You Find Other Electrical System Faults

It was mentioned under bad installations, but the alarm system can cause other electrical system faults.

Aftermarket alarm systems require tapping into the factory electrical system to trigger the alarm when the dome lamp illuminates or a door is opened.

They also use the battery connections to power the alarm when the car is turned off. The alarm can be triggered by the factory’s electrical system and cause other electrical faults.

How to Fix It

Aftermarket alarms can cause a headache when they are integrated with a factory electrical system. Installers can mistake a circuit that doesn’t show voltage to be a constant ground.

When the circuit does receive power, it can blow fuses or burn out light bulbs. If there is an installation issue that causes other faults, the installation needs to be checked circuit by circuit to ensure it is not causing other issues.

Secondly, corrosion can cause factory electrical system issues. It can cause short circuits, blown fuses, and systems to not work 100% of the time.

Aftermarket alarms can promote corrosion with various connectors added to the electrical system, and they should be cleaned and protected to prevent inducing electrical problems.

Read also, Car Voltage Drop Issues? 7 Common problems & Solutions

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