Audi A5 Alarm Going Off? (11 Common Causes)

The Audi A5 is a luxury small car that started out as a 2008 model year in the US.

Like many other vehicles, this model can suffer from alarm issues.

If your A5’s alarm keeps going off, this article contains valuable information…

Why Does My Audi A5 Alarm Keep Going Off?

An Audi A5 alarm is usually triggered by faulty door and trunk switches. Other common causes include issues with the hood switches, a bad 12V battery, and even key fob issues.

1. Faulty Door and Trunk Switches

Damaged, malfunctioning, wet, or dirty door and trunk switches are frequently responsible for spontaneous alarm activations by transmitting incorrect signals to the alarm system.

These switches are susceptible to wear and tear due to the regular use of doors, including opening, closing, and slamming.

The door latches and door switches can get dirty too which can cause issues, so the first thing you should do is give all door latches a good clean and spray some WD-40 on the latch and work it in to see if that helps.

Additionally, inspect the wiring that runs from the car’s body to the door for any signs of damage. Typically, this wiring is encased in a flexible hose located on the door’s hinge side.

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.

“ … there might be a loose connection on the door/trunk/hood sensors.” –

“Maybe broken wire in the harness at the driver’s door hinge area.” –

2. Faulty Hood Switch

A faulty hood switch frequently causes unexpected alarm activations in this particular model.

Normally, this switch is integrated into the hood latch mechanism.

This tiny electronic device, critical for the car’s alarm system, detects whether the hood is in an open or closed position.

Faults, looseness, or dirt accumulation in the switch can result in incorrect signals being sent to the vehicle’s computer, which in turn can activate the alarm unnecessarily.

  • Open the hood and locate the hood switch.
  • Check for any clear signs of damage, rust or loose connections.
  • Give the hood switch a thorough cleaning (with contact cleaner), as dirt and grime can cause issues.
  • With the right tools, you can test the switch with a continuity tester.

If you’re mechanically inclined, consider purchasing a new hood switch online and installing it yourself. Otherwise, it’s recommended to seek help from a local mechanic.

One owner mentioned this on the r/Audi subreddit:

“I’ve had this happen due to a hood latch switch on both of my Audis. Scanning it with VCDS should reveal what set the alarm off. All it takes is a slightly loose connection somewhere.”

Related: 11 Most Common Audi A5 Problems (Explained)

3. Loose or Bad 12V Battery Connections

Loose or incorrect connections to the 12V battery can result in a range of problems, including the unintentional activation of your A5’s alarm system.

These connections often accumulate dirt or corrosion.

The vibrations from regular driving can cause the battery terminals to become loose.

Always make sure to turn off the engine before conducting any battery maintenance.

Adhere to the following basic steps if you intend to conduct the assessment on your own:

  1. Examine the battery for any indications of wear, such as dirt, rust, or corrosion.
  2. Detach the battery, starting by loosening the clamp nuts with a wrench.
  3. Always disconnect the negative clamp, identified by a ‘-’ sign, first.
  4. Use a toothbrush soaked in a baking soda and water solution to clean the terminals. Rinse with distilled water and dry thoroughly.
  5. When reconnecting the battery, make sure the connections are secure and tight.

This is what one owner had to say on

“My first suspect is the battery. Knowing your car is a 2011MY, car batteries typically last for 6 to 7 years or even 10 if you are lucky…”

Here is what one owner mentioned on

“Could be your battery is starting to fail. Get the voltage checked.”

4. Drained 12V Battery

A depleted car battery can cause various problems, such as accidental alarm triggering.

It is recommended to have your battery tested for its condition, a service that is often inexpensive or complimentary at locations like AutoZone.

Alternatively, you can conduct a self-assessment using a multimeter (refer to the guide at the end of the article below).

Typically, a functioning 12V battery should register between 12.6 and 12.8 volts, whereas a failing one will show below 12 volts.

5. Key Fob Running on Low Battery

A low battery in the key fob is often behind unexplained alarm activations. Additionally, a dirty or dusty fob can lead to similar issues.

Cleaning the interior of your fob and changing its battery can help resolve these problems. Investing in a higher-quality battery brand is usually beneficial.

  • 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.

6. Faulty Key Fob

Another reported cause of nuisance alarms on this vehicle 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.

7. Incorrectly Installed Aftermarket Alarm and Accessories

Incorrect installation or defects in an aftermarket alarm system or accessory are frequent sources of bothersome false 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. 

“The alarm would go off for no apparent reason in the middle of the night. Turns out the issue was my Metromile insurance mileage tracker plugged into the OBD-II port…” –

8. 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.

9. Water Damage

Exposure to water or moisture sometimes causes short circuits or corrosion in the electrical wiring, leading to problems with the alarm system.

Identifying water damage in a vehicle’s electrical system can be complex and often necessitates a professional, such as an auto electrician, to perform diagnostic tests to pinpoint the issue.

10. 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 vehicle.

States such as Illinois, Indiana, Iowa, Texas, Wisconsin, and Carolina have large wild raccoon populations. 

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. 

11. 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 vehicle’s alarm. 

Alternative Suggestions

Check for Recalls or TSBs

By entering your car’s VIN number on Audi’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.

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 an Audi Dealership

If needed, take your Audi 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.

Related: Audi A6 Alarm Going Off? (11 Common Causes)

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.



  • 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...