Originally Posted by Voytek
Thanks Alex Avi,
I do not think we have a security aftermarket alarm system. We bought it used... It happens today during hot day, if was loud continuous horn like sound for about 5 min then sounded off. Car was locked and during siren I did unlocked it with fob open the doors everything inside was ok, loud horn sound was coming from around rear passenger side wheel base. No idea wat was causing it... Could it be faulty propane alarm? But no LP smell... I called Airstream dealer and they said it is probably MB problem and I should call MB dealer.
VOYTEK - OK, horn vs. siren sound - that matters because if it was horn sounding, then maybe it was the propane alarm. I don't think the MB ATA (even if yours came with it) utilizes a siren. Manual states horn sounding during activation. But when I accidentally trigger my interior propane alarm (which is on that rear pass side), it was a pulsing beep, not continuous. I have not read anything pointing to an exterior propane alarm. I have never heard my propane alarm from outside, so no idea how loud it is. You can trigger the propane alarm intentionally by blocking the inside sensor and maybe that will confirm if the sound is the same in pitch/volume. Also, AFAIK the propane alarm is not reset-able by the keyfob. Grasping at straws here - the subwoofer/amp is on that same side. I dont think that a subw is capable of that high a frequency, but a malfunction can still cause some audio??? This is indeed weird situation you are into.