The Model 3 is one of the most popular EVs on the road today.
Despite all its advanced tech and software, it’s still vulnerable to mysterious alarm problems just like any other vehicle.
If your Tesla Model 3’s alarm keeps going off, this article is here to help…
Table of Contents
Why Does My Tesla Model 3 Alarm Keep Going Off?
A Tesla Model 3’s alarm is usually triggered by faulty doors or software issues that cause bugs with the alarm system. Other common causes include trapped bugs, Tesla app issues, and problematic aftermarket accessories.
1. Sentry Mode
When Sentry Mode detects motion around the car, it can trigger the alarm to go off.
Sometimes, even harmless things moving around the car can create false positives such as:
- Flickering lights
- Leaves or branches
- Other vehicles
If you’re parked out in public, false alarms are more likely to happen.
Here’s how a few owners on the TeslaMotorsClub.com forum described their experience:
“I had an issue with the car alarm going off all the while and put it down to being parked in a field with grass and trees waving in the wind.”
“Mine is set off by a street light flickering when the tree in front of it sways in the wind. When it’s parked facing away from the street light it’s fine.”
Loud noises such as rumbling engines, construction work or thunderstorms can also trigger Sentry Mode to start recording and set off the alarm.
If you receive a notification on your phone saying “Sentry Mode has triggered the alarm state” this means your alarm has gone off.
You can always check the footage on the App to see if there’s something suspicious going on with your car when you see these notifications.
If Sentry Mode is always triggering the alarm even if you’re parked in a secure location such as your garage or driveway, you can always just turn it off until you find out the root of the problem.
You can also turn off the cameras by toggling Camera-Based Detection in the Sentry Mode settings.
Even with cameras off, Sentry Mode will still record footage and the alarm will still go off if the tilt and intrusion sensors are triggered, like when someone accidentally bumps into the car while it’s parked.
If all else fails, try removing the USB drive you use for Sentry Mode as some drives can cause random issues.
2. Software Glitches
In some cases, a software glitch or a buggy software update can trigger the alarm more often.
To clear out any possible glitches, you can try resetting the car’s computers.
To perform a reset, follow these steps:
- Press and hold the two scroll wheels on the steering wheel
- Wait for the screen to turn off
- After a few seconds, the touchscreen should restart on its own
You can do a soft reset even while the car is moving and the car should still drive normally. But it’s always better to do it while safely parked on the side of the road.
Disconnecting the 12-volt battery will also power down the Model 3’s computers and force a full restart once the battery terminals are reconnected.
Leaving the car for a while so it can go into a deep sleep state can also clear out software glitches.
Some software updates can also mess up features that were working fine before such as the Sentry Mode and alarm.
If you contact Tesla, they can sometimes manually force a software update to get rid of the problems the previous software version caused.
Here’s how two owners described their experience on TeslaMotorsClub.com:
“My Model 3 has developed an annoying fault in that the alarm sounds briefly when I unlock it (Android phone) and open the door after it has been asleep for several hours. Not good for my neighbors at 7 am. A reset doesn’t help. Anyone else have this problem?”
“Yes, it’s very very annoying, it’s only appeared a couple of days ago since the last update so I assume it’s some bug in the software as the car’s been fine for over 2 years. I believe several others have been experiencing the same problem.”
3. Bugs Inside the Cabin
Teslas are no stranger to bugs since they’re basically a computer on wheels, but we’re talking about actual insects or tiny critters getting stuck inside and triggering the Model 3 alarm.
It may sound unlikely, but it’s one of the more common causes of false positives, especially with the Model 3’s sensitive alarm sensors.
One owner on the SpeakEV.com forum had this to say:
“My M3 alarm went off recently and, when I went to investigate, I could see no reason why that might have been – until I got into the car. A wasp was trapped inside. There was no other apparent reason for setting off the alarm and, once the wasp had been removed, the alarm did not trigger again.”
Other owners on the r/TeslaModel3 subreddit had similar problems:
“Had my M3LR for 18 months now. Since the last few weeks, the alarm is acting crazy, triggering at random, and multiple times in a row, in different parking places. Deactivating Sentry does not help. Tesla Service confirmed that small insects can trigger the alarm.”
“The second time the alarm triggered was on the same day after I parked it for a couple hours with sentry on and all of a sudden it triggered alarm state again with the horn and all. All I found was a rather big green insect inside the car.”
To get rid of any insects inside the car, try the following:
- Leave the doors and windows open for a while
- Vacuum inside the car
- Use bug repellent or bug traps
To check whether something inside the car might be triggering the alarm, turn off the Tilt/Intrusion sensor.
This setting can be accessed by going to Controls and then selecting Safety.
In some cases, an expanding plastic water bottle when the car is parked in the sun can also cause the alarm to go off.
Checking Sentry Mode will also sometimes let you know what caused the alarm to go off. If all else fails, Tesla service can check which sensor is triggering the alarm.
If you need to leave the car with passengers or pets inside, you can turn on Dog or Camp mode. If the car is being transported, you can also put it into Transport mode to keep the alarm from going off.
4. Preconditioning or Remote A/C
The Model 3’s alarms can be triggered by its blower fans, A/C compressor or heat pump.
Turning on the HVAC remotely or setting a preconditioning schedule for the car causes enough noise and vibration to trigger the alarms.
Here’s how one owner on the TeslaMotorsClub.com forum described their experience:
“For the last week or so every time I start the A/C from the app on LR M3, it triggers the Sentry Mode alarm.”
If you want to avoid triggering the alarm when remotely turning on the A/C, you have to remember to turn off the Tilt/Intrusion sensors. The same goes if you want to set a preconditioning schedule.
The Model 3’s Cabin Heat Protection feature can also trigger the alarm when temperatures go up so it’s normally disabled if you have the Tilt/Intrusion sensors turned on.
In some cases, the false alarms only go away once the Cabin Heat Protection is disabled, but software updates can usually fix these inconsistencies.
5. Faulty Door Handles or Latches
The Tesla Model 3’s door handles and latches can become faulty and cause false alarms when they don’t fully close or try to open by themselves.
Here’s how owners on the r/TeslaModel3 subreddit described their experience:
“2020 LR AWD. Frunk is open warning was triggering false alarms. Fix was Tesla service replacing a faulty frunk actuator.”
“The frunk alarm used to go off every time it gets hot outside. Made a Service appointment and got the latch replaced. No issues since.”
Another owner on the r/TeslaMotors subreddit had this to say:
“The car alarm has triggered falsely 2 times this week on my model 3, once on my driveway just minutes after I parked the car (no one around). I noticed a few times that one of the door handles does not close automatically, it kind of stays open and might close itself slowly later.”
Lubricating the door handles and/or latches with WD-40 or silicone grease can sometimes knock out the built up debris inside the door handles and make them operate smoothly again.
This should prevent them from getting stuck and inadvertently causing the alarm to go to off.
If cleaning and lubricating doesn’t work, you’ll most likely have to replace the handles or the latches.
All of this also applies to the boot lid and the frunk.
6. Faulty Sensors
A malfunctioning sensor can easily cause the Model 3’s alarm to go off for no reason.
A faulty sensor is much more difficult to diagnose service so you’ll probably have to get Tesla Service to look at your vehicle.
Sometimes, a diagnosis can be made remotely by simply looking at the car’s logs.
If the problem persists, an actual tech needs to physically check the sensors and the car for themselves.
One owner on the r/TeslaMotors subreddit had this to say:
“Alarm randomly goes off when locked (sentry mode on or off) and open frunk being detected which prevents autopilot use. M3P with 2020.20.12.”
7. Weak 12-volt Battery
A weak 12-volt battery can cause a lot of strange electrical issues in the model 3, including more frequent false alarms.
The Model 3’s infotainment and a lot of its computer systems run off the A lot off 12-volt battery.
Normally, this gets charged by the large EV battery every time you drive.
If you let the Model 3 sit or if the car’s 12-volt battery is already 3 or more years old, it might be too weak to hold a charge.
Batteries can also wear out within a year due to manufacturing defects.
If you suspect the 12-volt battery is dying, you can have it tested at an auto parts store, or just simply spring for a new one.
Here’s what one Model 3 owner experienced on TeslaMotorsClub.com forum:
“The battery was low (not the main battery, but rather the ‘standard’ battery you get in an ICE car – This is known to cause issues with the alarm, and so a long drive would charge and resolve – This is my leading theory! The car has been sat idle for 5-10 days on the drive.”
8. Aftermarket Accessories
Faulty or incompatible accessories like USB devices, lights or aftermarket frunk openers can cause the Model 3’s alarm to go off at random.
Here’s what one owner on the r/TeslaMotors subreddit had to say:
“My alarm keeps randomly going off without me doing anything, and the front trunk pops open. Keep in mind the front trunk is not stock and has a power open option that the dealership put on.”
Unplug all the non-stock parts from the car and observe if the alarm is still triggering on its own.
9. Tesla App Issues
The Tesla app on your phone can sometimes run into glitches and cause random issues with the alarm.
To fix these software bugs, try the following:
- Toggle your phone’s Bluetooth on and off
- Restart your phone
- Make sure the Location settings for the app is set to Always
- Reinstall the Tesla app
- Remove the phone by going to the Controls and then Locks setting
You can also toggle the Walk Away Door Lock feature and manually lock the car instead using your phone or key fob.
If you have the Exclude Home feature enabled for the locks, make sure your saved locations are correct.
10. Weak Key Fob Battery
A weak key fob battery can cause issues with how the car’s locks and alarms work.
You can always try replacing the key fob battery even if they’re just a year or so old since they’re very cheap anyway.
The installed battery may have been defective from the factory or an old one that’s been kept in stock for too long.
To replace the Model 3’s key fob battery, follow these steps:
- Pry open the battery cover using a small flathead screwdriver or similar tool
- Remove the old battery
- Wipe the insides of the key fob even if it’s fairly clean
- Insert the new battery with the flat side facing towards you
- Reinstall the battery cover
11. Key Fob Issues
A faulty key fob can be the main culprit of your Model 3’s alarm problems.
Sometimes, simply placing the key fob next to something that could interfere with its signal like your phone can cause it to act up.
You can also unpair the key fob from the car temporarily and see if that fixes the alarm issues.
While you’re observing the problem, you can use your phone or key card to unlock and drive the car.
If you’ve narrowed down the issue to the key fob and you’ve already replaced the battery, you can get a new one through the Tesla online shop.
Check for Recalls or TSBs
Check for recalls for your vehicle by going to the NHTSA or Tesla Service recall page to see if there are any outstanding issues with your car that may affect the alarm system.
Entering your VIN on the NHTSA website’s Safety Issues and Recalls page will also show you a list of TSBs (Technical Service Bulletin) for your specific vehicle. Look out for any known problems with the doors, electronics or software that may be related to your alarm issues.
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.
Check the Wiring
Loose electrical connectors and broken wiring harnesses can cause mysterious alarm problems.
Wiring issues are more common in the following scenarios:
- After having the car repaired
- If the car has been damaged due to an accident
- Previous incidents of water intrusion
- Corrosion due to age or lack of maintenance
Check the 12-volt battery terminals and make sure they are properly bolted down. If you see any debris or corrosion on the terminals, clean them out first.
You can also check any exposed wiring for any obvious signs of damage or wear.
Check the Car’s Logs
Aside from asking Tesla Service, you can check your car’s logs by using third party apps like TeslaFi or TeslaMate.
This should give you a more detailed view of what’s happening whenever the alarm is triggered.
Schedule a Service Appointment
If you’ve run out of ideas trying to troubleshoot the problem on your own, you can schedule a service appointment through the Tesla app.
You can either take it to the nearest Tesla service center or have a mobile tech come out to your location.
Once you schedule an appointment, you can start talking to a representative about your problem.
If you’re able to resolve your issue after consulting with a representative, you won’t be charged for the service as long as you cancel the appointment at least 24 hours in advance.
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.
- Power down the car and leave it unplugged for several hours
- 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.