I have a 05 hyundai sonata. I put a new battery in now the alarm goes off and I don't have a remote. Car wont start

have you tried locking and unlocking the car with the remote. How about locking and unlocking the drivers front door with the key?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

You are most likely correct, it probably has an alarm. Unfortunately, most alarm systems are connected to the remote that is broken. You should have to have your dealership get you a new remote for the vehicle.

The battery in the remote maybe flat, replace the battery with a new one.

Your Sonata is equipped with a "Keyless Entry & Burglar Alarm" system. When the Burglar Alarm is activated, it KILLS the starting system through the used of a relay called the "Burglar Alarm Relay". This mode prevents engine starting with the key.
Solution #1
Disarm the system with the Keyless Remote (key fob) If you don't have this remote (or its battery is dead) replace the battery & try disarming again.
Solution #2
Enter the vehicle & insert the key in the ignition and turn the ignition switch to 'RUN'. Wait 3 to 5 minutes until the alarm stops. You should then be able to start the engine.

Have a qualified/certified Hyundai Service Technician properly diagnose this issue.

I know this sounds obvious, but did you run your battery dead? If you don't know, get the battery checked.as for as tuning off the alarm... Just simply disconnect your negative battery cable. This will reset the alarm. This doesn't solve the problem but makes it less annoying while figuring it out. What about the battery in your remote, is it dead? Look for any wires from the alarm that may be frayed, cut, or corroded. Hope this helps.

The 2003 Sonata is equipped with a 'starter KILL' burglar alarm system with disables the starting system (using a N/C 'contacts' configuration instead of a N/O contacts configuration). N/C=Normally closed, and N/O=Normally open contacts. When the alarm goes off with a MY Sonata, the only way to DISARM it is with the key fob (remote) originally programmed for it (unless you purchase a new remote & have it programmed for the vehicle at an authorized Hyundai Service Department). NOTE: So long as the keyless entry & burglar alarm system is functioning/operating normally, the alarm will keep going off and the STARTER KILL function will still prevent you from starting the vehicle. One option is left without purchasing a new remote and having it programmed.
1. When the alarm goes off, get into the vehicle and insert the ignition key into the ignition.
2. Turn the key to the 'RUN' position (NOT the ACC position) and wait for the alarm to STOP (usually about 3 to 5 minutes).
3. The engine should then start using the ignition key.

If this procedure doesn't work, the problem will need further diagnosis by a qualified/certified Hyundai Service Technician.

Hope this helps

Yes!... reset the alarm with the fob!

Sounds like you have a shorted wire causing a drain. I recommend disconnecting the alarm all together which should stop the short so battery can remain fully charged.

When the alarm is activated, there is an Anti-Theft device (Starter Kill Relay) which prevents anyone from starting the engine using the key (about 5 minutes). If you place the key in the ignition and turn the key to the "RUN" position, wait 5 minutes (approx), the engine should then be able to start. If not, the problem may be the ETACS (Electronic Time & Alarm Control System) module. If it does start, the problem may simply be that the battery in the keyless remote is weak/dead, or the remote needs to be programmed again for that vehicle. Only the remote can 'DEACTIVATE' the alarm. Best solution, take/tow the vehicle into a Hyundai Service Center (dealership), pay the diagnostic fee. They will tell you EXACTLY what the problem is and what's needed to fix it (parts, labor, tax, time-frame, etc.).

One word:

Dealer.

Next time just disconnect the battery until you get it towed as this is a warranty item. I'll bet some wondered if this was a prank question like I did, right?