2007 Honda Accord, Enable Factory Alarm or Identify No Name Alarm

Hi first post. I found this aftermarket alarm that was installed by the dealer on my 2007 Honda Accord 4 door. They put a Viper 330V manual in the car but this isn't a viper. The wires in the manual don't match the brain. Very sketchy since I don't even have a guide of which triggers match to the respective led flashes. The car has a factory alarm but they added this one to upcharge the vehicle price. It used to work ok, but now it goes off randomly when the sun hits the car in the morning or afternoon but never at night, thank goodness. I traced every lead and it looks like it is a voltage sensitivity issue. On a test bench, I was able to confirm that when there is a slight (ie. a dome or courtesy light turning on) the alarm triggers. On my bench I just hooked up a small 12v bulb on the power lead and could get the alarm to trigger. I'm assuming this alarm brain monitors voltage changes. I changed the car battery to a brand new one and it's still behaving badly. The alarm only monitors the doors and has a shock sensor. Interestingly, the trunk and hood are not wired. The alarm reports flashes for the last 2 trigger events and 1 flash is the shock sensor and 3 flashes are the doors. The false alarm trigger is 2 flashes and I can replicate it if I turn on the interior lights or the headlamps. None of the alarm wires go to any lights. There was one wire that flashed the parking lights but I cut that wire and it still false alarms. I don't see any bulging capacitors or issues on the alarm brain board.

The alarm uses the factory key and it arms and disarms through the door lock/unlock wires. The immobilizer works fine. Other than that, it has 12v power, ground, ignition, siren, led and valet button leads only connected. I'm also stumped because when I removed the alarm for testing on my bench, I can't get the factory alarm to work. I verified the dash light for the factory alarm works through the Honda diagnostic test which flashes all the indicators on the dash. I checked the driver side door switch and don't see anything that was modified there. Under the dash, everything was t-tapped so nothing going on there. Obviously, I'm missing something but you guys must have a better idea.

So I'm stumped and want to either adjust (dip switch setting?) the aftermarket alarm's voltage sensitivity which I can't find any information on or get the factory alarm reinstated. Thoughts?

Thanks in advance,

Jon

proxybox wrote:

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The car has a factory alarm

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Why do you think that? It's not common to install a basic aftermarket alarm on top of a basic factory alarm.

You can try putting a capacitor in parallel to the constant 12v supply to the module to smooth out/dampen any voltage dips.

We bought the Accord new from an auto broker who sourced the car from a dealer and they contracted with an alarm shop to install the alarm as a bonus. I went to the alarm shop and they insist it's the shock sensor sensitivity that's causing the false alarms and they turn it down to adjust but the behavior persists. I asked them for the manual but they said they don't have any because it is so old. I asked why there was a Viper manual but they shrugged.

Your question made me question my assumptions which is great. I did some digging and I have an Accord LX. According to the manual and the Honda website, the LX did NOT come with a factory alarm. Argh, I assumed it had one because the manual shows the indicator and also a section on the alarm. However, when I read more carefully, it does say for models other than the LX. I appreciate your question.

Great idea on the capacitor. What size do you think? Should I also add a diode?

Other than that, can you recommend an inexpensive brain to replace this one? I want to still have it arm via the door wires so I can keep my factory key.

My neighbors and I thank you!!!

@catback Your information was much appreciated! I researched how capacitors work here: https://youtu.be/X4EUwTwZ110 and recognized that the voltage rating was the maximum voltage the capacitor could handle. I ended up purchasing a 25v 2200uf electrolytic capacitor for $2 and soldered the positive lead to the 12v supply and the negative lead to the ground wire as you instructed. When I plugged the leads to the car it sparked so I was a bit concerned but that's probably the inrush to charge the capacitor. Once installed, I pulled power from the circuit and I could see voltage still holding within the alarm box with my volt meter. Yeah! Finally, I armed the system and turned interior lights on and everything was rock stable with no false alarms. I really appreciate this because I learned a ton while researching this.

Thanks again!