Beware the hood sensor and tail gate sensor - both are likely suspects.

I'd be interested whether you paid any special attention to the dash lights when you went out to disarm previously, or did you just use the fob without getting in and checking the dash? There's no special indicator for the hood, but there is for the tail gate if it's still not latched by the time you get there.

Sounds like it's more likely when it's colder, so when it is, but when the neighbors aren't likely asleep, it would be worth trying to give a good yank on both the hood and the tail gate to see if you can trip the sensor on either while they are (ostensibly) latched and set off the alarm. Neither should respond..

 

I tried pulling on all doors hood and tail gate and could not trigger the alarm. I did not check any of the dash lights. At 2am my first goal was to turn off the alarm.

 

Understood. You don't need irate neighbors! Post above is certainly interesting -- a symptom of that bad ground that we had not year heard, and I think we've heard them all here before at one time or another. Have a look at this TSB for reference (attached). It addresses different symptoms, but the same problem source.

 

I had the same problem with the alarm going off randomly after it rained. Traced the problem to negative battery cable connection to the painted fender well. The connection was thru 2 small screws the were corroded. I scraped the paint off and cleaned the screws to fix the problem. This also also solved intermittent problems with outside temp display.

 

@deesperson
Indeed, that bad ground can cause a whole host of interesting gremlins, though I think this is the first time we've heard that the alarm system can be one of the results. While Hyundai does not recommend scraping off the paint, I do. After chasing the threads, cleaning it up, and taking off a bit of paint under the lug, just be sure it's goobered up with plenty of your favorite material that will prevent any corrosion after the fact. I often mask off the area and hit it with one of the products used for 'painting' battery terminals. Others use various types of grease.

 

I had the same night alarm went off, found the hood lock sensor was wrong.
Alarm system went off when the hood lock sensor detect the hood was open.

Instead of replace the sensor, simply I disconnected the sensor wire connector located just under the hood lock.

 

I thought about that as well. I disconnected it and it was fine for one night but went off the second night. It would be nice if somehow you can identify what sensor is triggering the alarm.

 

Hood switch(or sensor)& connector is around hood lock, above the radiator.
When hood/door/tailgate is closed, the switch circuit is open(unlimited ohm).
so disconnection of the switch means ALWAYS closed.

===========
BURGLAR ALARM SYSTEM
The burglar alarm system is armed automatically after the doors, hood, and tailgate are closed and locked.
The system is set off when any of these things occur :
• A door is forced open.
• The tailgate is opened without using the key.
• The hood is opened.
When the system is set off, the alarm sounds and the hazard lamp flash for about 30 seconds or until the system is disarmed by unlocking the transmitter.
For the system to arm, the ignition switch must be off and the key removed. Then, the body control module must receive signals that the doors, hood, and tailgate are closed and locked. When everything is closed and locked, none of the control unit inputs are grounded.
The door switches, hood switch and tailgate switch are all close and lock the doors with the remote transmitter and then the system arms immediately.
If anything is opened after the system is armed, the body control module gets a ground signal from that switch, and the system is set off.
If one of the switches is misadjusted or there is a short in the system, the system will not arm. As long as the body control module continues to get a ground signal, it thinks the vehicle is not closed and locked and will not arm.

 

As its an evening nighttime issue.

Have you considered or addressed this is not the fault?

 

They were on the news the other day. Taking the Toronto subway walking on the platform with the people. Without a care in the world. I wouldn't be surprise is wasn't a B&E **** tripping the alarm. If he start it after would really be something.

 

2009 Santa Fe. I'm having the same issue, alarm is going off at random times. Can I just cut the red/black cables going to the hood switch to fix the problem? This way, the car will think that the hood is constantly open, therefore not arming the alarm? The horn died years ago from this problem, and I've lost many batteries because of it. Very annoying, and I'm very broke so I can't take it to a shop to get it fixed. Just got a new battery today and the problem persists. Any way to prevent the alarm from arming would be good as well.

 

Can I just cut the red/black cables going to the hood switch to fix the problem? This way, the car will think that the hood is constantly open

You've got that the wrong way round. The hood switch is open when the hood is closed, so cutting the wire would make the car think the hood is constantly closed.

If I helped you fix it, why not...

Your support is greatly appreciated​

 

My last post is still awaiting approval by mods but it reads:

Alright thanks, then I can cut those wires and solder them together, correct?

 

You can either link the two wires together, or it might be easier to just unbolt the complete switch and leave it plugged into the harness. If you zip tie the switch in the engine bay somewhere so the hood isn't able to press the button that would make the alarm think the hood is permanently open.

If I helped you fix it, why not...

Your support is greatly appreciated​