Chevrolet Blazer Alarm Going Off? (12 Causes & Solutions)

The Chevrolet Blazer is a sporty-looking midsize SUV.

Like any vehicle, the Blazer can suffer from car alarm-related issues. 

If your Blazer’s alarm system keeps going off, this article is here to help.

Why Does My Chevrolet Blazer Alarm Keep Going Off?

A Chevrolet Blazer alarm is usually triggered by a faulty door switch or hood switch as these sensors are prone to defects or damage after several years of use. Other common causes include battery problems, key fob issues, and a faulty body control module (BCM).

1. Malfunctioning Door Switches

Faulty door switches (including the rear hatch) are a common cause of random alarms on the Blazer. These switches monitor the open/closed status of the door – if damaged, faulty or dirty they can send false readings thereby triggering the alarm.

Door switches are a common point of failure as they are subject to wear and tear due to the doors being continually opened/closed/slammed etc.

  • The door latches and door switches can get dirty too which can cause issues.
  • Give all door latches a good clean and spray some WD-40 on the latch and work it in to see if that helps.
  • Check the wiring leading from the body into the door for any signs of damage, it should be in a flexible hose on the hinge side of the door.

If you suspect the alarm issues are linked to the door switch, ask your dealer to run a diagnostic test to try and pinpoint the fault.

“It could also be a bad door switch. I had that problem on a 2000 bravada. So when its locked it will randomly think the door is being opened causing the alarm to go off” – BlazerForum.com

“Since the passenger door doesn’t get used as much as the drivers door, check to see if the switch is not just stuck…” – FixYa.com

Note: Rust and corrosion can also damage the latches and switches, which may trick the sensors into thinking a door is open.

2. Faulty Hood Switch

A faulty hood switch is a common cause of unwanted alarms on many vehicles, including the Blazer.

The switch is typically embedded in the hood latch.

The small electronic device is designed to detect whether the hood is open or shut and is an important part of the car’s alarm system – if it is broken, loose or dirty it can send false readings to the car’s computer thus triggering the alarm.

  • Pop the hood and locate the hood switch.
  • Check for any obvious damage, rust or loose connections.
  • Give the hood switch a clean too (use contact cleaner), as dirt and grime can cause issues.
  • You can test the switch with a continuity tester.

If you are well-versed mechanically, you can buy a new hood switch online and replace it yourself. Otherwise, we’d advise visiting your local mechanic.

Related: Chevrolet Blazer Beeping? (13 Common Causes)

3. Loose or Bad 12V Battery Connections

Loose or bad 12V battery connections can cause a number of problems, including triggering the alarm of your Blazer.

A bad connection can be caused by dirt or gunk buildup.

The terminals may have come loose from driving and vibrations etc.

Make sure the engine is off before doing any work on the battery.

  1. Inspect the battery and look for any signs of damage, dirt build-up, rust, or corrosion.
  2. Disconnect the battery and loosen the nuts on the clamps using a wrench.
  3. Remove the negative clamp, marked with a – symbol first.
  4. Clean the terminals with a toothbrush dipped in a mix of baking soda and water, rinse with distilled water and dry with a cloth.
  5. Reconnect the battery, ensuring tight connections.

“Check that the battery terminal connections are tight…” – BlazerForum.com

4. Drained 12V Battery

A faulty or weakened car battery causes a variety of problems, including accidentally triggering the Blazer alarm.

The best thing to do is take your Blazer for a battery health check, these are usually quite inexpensive or sometimes free such as at AutoZone.

Or you can test it yourself with a multimeter (see the guide at the end of this article).

A healthy 12V battery should be about 12.6 to 12.8 volts while a weakened battery reads below 12 volts.

5. Faulty Key Fob

Another reported cause of nuisance alarms on the Blazer is a faulty key fob.

If you have 2 remotes, try taking the battery out of one and use the other for a while.

If the alarm problems persist, and you have tried cleaning the inside of the fob(s) and changing the battery, the best thing to do is speak with your dealer.

6. Key Fob Running on Low Battery

A common cause of mysterious alarms on the Blazer is a low key fob battery. Similarly, if the fob is dirty or dusty this can also cause alarm issues.

Give the inside of your fob a clean and replace the battery to eliminate this possible cause. It’s worth spending a bit extra for a good brand of battery.

  • To open your key fob, stick your prying tool into the slit or gap between the two halves of the outer casing and gently apply upward pressure to pop open the device.
  • Remove the battery.
  • Give the key fob a good clean to remove any dirt or fluff – a cotton swab and some rubbing alcohol should do the trick.
  • Check for damage, rust or loose connection (you may need a new key fob depending on what you find).
  • Be sure to insert the new battery facing the right way up.
  • Assemble the outer casing of your key fob by clamping them back together.

7. Incorrectly Installed Aftermarket Alarm

An incorrectly installed or faulty aftermarket alarm system is a common cause of nuisance alarms.

Aftermarket alarms are typically far more complex than any factory-installed equipment which makes them more prone to issues.

They may also have been installed by incompetent individuals.

If you are experiencing issues with an aftermarket alarm, the best thing to do is speak with a reputable auto electrician. 

8. Damaged Body Control Module

A faulty body control module can cause a wide range of issues including nuisance alarms.

  • The BCM is in charge of electrical communication from different electronic systems.
  • This includes the car alarm system, lock-unlock functions, climate control etc.

If your alarm system has randomly been going off, alongside several other electrical issues (random honking, locking/unlocking on its own, unresponsive key fob), have your vehicle checked immediately.

This was suggested by one owner on the r/MechanicAdvice subreddit:

“You can yank the TBC fuse to cut power to the body control module, but this will also make it so nothing works. Your BCM is most likely failing though, could have had some water sneak its way into it and corroded a part of the board.”

9. Water Damage

Water leaking into the vehicle’s electrics and latches can cause issues.

You will need to visually inspect your car and look for any signs of water ingress.

Around the door seals are a good place to start.

10. Damaged Wiring

Damaged electrical wiring can cause a wide range of problems, it can often be tricky to pinpoint too and you may need to have an auto electrician run some diagnostic tests.

In some instances, rodents may have chewed through an electrical wire.

“sounds like your alarm system went poof or theres a short somewhere in the alarm” – BlazerForum.com

11. Animals Climbing On The Vehicle

If your alarm has been set off in the middle of the night, it may have been by an animal climbing on the car.

Have a look for footprints on the hood and the roof. 

If you have a CCTV system, examine the footage. These animals usually appear during the night. 

12. Not Closing Doors, Hood, or Trunk Properly

Something as simple as not properly closing the doors, hood, or trunk will inevitably trigger the alarm.

Make sure to check if you have closed every point of entry of your vehicle to avoid accidentally tripping your Blazer’s alarm. 

Alternative Suggestions

Check for Recalls, TSBs and Software Updates

By entering your car’s VIN number on Chevrolet’s recall page or the NTHSA’s Safety Issues & Recalls page you can determine whether or not there is a TSB or recall for your vehicle and if there is you’ll want to get it addressed.

A recall is issued by a vehicle manufacturer for issues that are safety-related, while a TSB covers components that may be malfunctioning but don’t compromise the safety of the vehicle.

Some vehicles require routine software updates to ensure everything works as it should, ensure you have the latest software installed.

Disconnect the Battery

Sometimes mysterious alarm problems can disappear with a simple reboot, there are no guarantees here but it’s worth a try.

Disconnect the battery for 20 seconds and this resets many of the electronics in the vehicle.

Check For Warning Messages

When the alarm occurs can you see any lights or warning messages on the instrument panel?

This can give a clue as to what’s causing the alarm e.g. ‘Hood Ajar’.

Take it to a Chevrolet Dealership

If needed, take your Chevrolet to the dealership.

Tell them you are NOT paying for a check on what the problem might be.

Ask them if they will check it for free.

Most dealerships and other places do quick/initial diagnosis for no money as they plan to make money for the repair of your vehicle.

If your unit is still under warranty then they should fix and resolve the issue for free.

How to Test the 12V Battery

How to Test the Battery:

  • Before testing, remove the surface charge from the battery, this allows for an accurate reading.
  • Simply turn on the headlights for 2 minutes then turn off.
  • Set the multimeter dial to the ’20 Volts’ setting.
  • Make sure the car is turned OFF.

The multimeter will have a red probe and a black probe.

  • The red probe is for making contact with the positive terminal.
  • The black probe is for making contact with the negative terminal.

Measure across the battery terminals.

  • The meter should display a reading, if the battery is fully charged the voltage should be between 12.2 and 12.6 volts.
  • Anything under 12V and the battery should be charged or replaced.

Related: 15 Best & Worst Chevrolet Blazer Years (Facts & Stats)

Sources

https://www.chevrolet.com/support/vehicle/manuals-guides

https://www.chevrolet.com/ownercenter/recalls

Author:

  • Ian Sawyer

    Growing up with a father who was a mechanic I had an appreciation for cars and motorcycles from an early age. I shared my first bike with my brother that had little more than a 40cc engine but it opened up a world of excitement for me, I was hooked. As I grew older I progressed onto bigger bikes and...

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