Your Mercury Grand Marquis’s alarm system is designed to detect potential intruders, keep its contents safe, and keep them from driving your car away. However, it is not uncommon for a car alarm to go off, or keep going off, for no apparent reason– also known as false or “nuisance alarms”.
This article will discuss some common causes of nuisance car alarms and what you can do to diagnose and prevent them in the Mercury Grand Marquis.
If your Grand Marquis’s alarm keeps going randomly off, you should first block the signal from your key fob and see if that stops it.
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Mercury Grand Marquis Alarm Going Off Causes
While there’s a lot to your Mercury Grand Marquis’s alarm system, it’s usually a sensor issue when it randomly goes off. The alarm is receiving a panic signal from the fob when you aren’t pressing any buttons.
A worn or damaged key fob can cause your Grand Marquis’s alarm to go off randomly. To prevent this from happening, check your key fob periodically and replace it if necessary.
The best way to check your key fob is to take it far enough away from your vehicle that they can’t detect one another anymore. Even if your Mercury Grand Marquis’s key fob isn’t working, it can still set the alarm system off.
Faulty Alarm Sensors
A faulty or damaged sensor is among the most common causes of nuisance car alarms.
A car alarm’s sensors are designed to detect motion, vibration, and shock, so a defective or old sensor may trigger a false alarm if it is not able to sense correctly.
The best way to determine if a sensor is causing your alarm to go off is to test each one individually. Car alarm systems have a combination of the following sensors (older cars will use less).
- Motion Sensors
- Vibration Sensors
- Door lock sensors
- Shock Sensors
- Magnetic Switches
- Ultrasonic Sensors
- Laser Detectors
- Hood latch sensors
Door Lock Sensor
Of these alarm system sensors, the most common issue that causes the alarm to go off at unwanted times with the door lock sensor. It tells your Mercury Grand Marquis’s alarm controller whether or not the door is locked. It’s usually connected to or part of the power door lock actuator.
If your car’s alarm keeps going off when you open the door, the door lock sensor still thinks the doors are locked.
Also, some vehicles don’t like to be opened with their keys. Using the unlock button on the key fob will likely remedy the situation.
Hood Latch Sensor
Your Mercury Grand Marquis may be equipped with a hood latch sensor designed to detect whether the hood is open or closed. If this sensor malfunctions, it can trigger a false alarm.
Due to where a hood latch sensor lives in your car (under the hood), it’s common for it to get dirty. Try cleaning the hood latch and sensor (you should see a sensor with wiring right by the hood latch).
Another common cause of car alarms going off randomly is a low battery. A weak, dying, or dead battery may be unable to power your Mercury Grand Marquis’s alarm sensors, resulting in false alarms.
The only way to know if a weak battery is causing the alarm to malfunction is to have it tested. Any local parts store should be able to test and replace your car’s battery if needed.
If the wiring of your Mercury Grand Marquis’s alarm is not correctly connected or insulated, it can cause false alarms.
To prevent this from happening, have a professional inspect and repair any faulty wiring, particularly if you are using an aftermarket alarm.
Interference from Other Devices
Modern devices such as smartphones and Bluetooth speakers can interfere with your Grand Marquis’s alarm sensors, resulting in false alarms. To prevent this from happening, keep any potential interference-causing devices at least 10 feet away from your car’s alarm.
Incorrectly Installed Aftermarket Alarm
If you have installed an aftermarket alarm system in your Grand Marquis, it may not be properly configured. This can cause the alarm to go off for no reason at all.
To prevent this, follow the installation instructions carefully and have a professional install the system if necessary.
How to Fix a Car Alarm that Keeps Randomly Going Off
If your car’s alarm keeps going off randomly (as in the middle of the night), getting it fixed before your neighbors decide to disown you might not be a bad idea.
Here are some steps you can take to fix an alarm that keeps going off in the Mercury Grand Marquis:
- Check the batteries in your vehicle and key fob. Replace them if necessary.
- Inspect all sensors and replace any that are damaged or worn out.
- Check for any potential radio frequency interference from nearby devices.
- Try blocking your key fob from talking to your Grand Marquis. You can use aluminum foil and put the fob as far from the house as possible. If the alarm stops going off, leave one key fob out until you figure out which key fob is malfunctioning.
- Have a professional inspect and repair your car alarm system if needed.
- Set up a game camera, or camp out to see if anything sets off the alarm. You could have a sensitive sensor, and an animal is setting it off.
If you are positive that nothing is setting off the alarm randomly, check your Mercury Grand Marquis’s owner’s manual for how to disable the alarm system if you can live without the added vehicle protection.
If your Mercury Grand Marquis’s alarm keeps going off, it is important to determine the cause of the false alarms in order to prevent further issues and protect your vehicle. Examining the above common causes and taking the necessary steps to fix them can help ensure your car alarm is working correctly.