efonz

Yesterday I went to Pepboys and got a new battery for the E. (It is the correct group 49 Bosch battery) So installing it went as planned
and everything seemed chill until my alarm starting acting crazy going off and sometimes refusing to turn off, also the indicator lights
would trigger and start flashing right before and during as well as after the alarm would trip. I got the battery yesterday at around 4PM
and the alarm problem didnt start until around 11PM the following day.

What do you guys think, is it related to the new battery or just a coincidence that I need to replace the module that controls the alarm?

I just read another thread about battery drain and now I am thinking that I changed my battery due some faulty module or leaking alarm
mechanism and its soon going to kill my new battery, but I didnt have any alarm related issues prior to changing the battery.

Anyone been through something like this?

I had to disconnect the battery and plan to reconnect it in the morning

kajtek1

Are you talking theft alarm?
Sounds like coincidence to me, but I would display car voltage on the cluster and observe it during driving.
Double check trunk and hood closure.
You can also push tow button before arming the car, what would point if that is tilt sensor, or door switch alarm.

rcmlndz

Look at the siren module behind the front fender liner, driver side. They are known for corrosion inside on the board. That happened to me. The would randomly activate the alarm no reason at all. Sometimes it would drain the battery down because the siren didnt make any sound. I removed the siren module and everything is good.

efonz

So I have been monitoring the battery using MBII but since I just got a new battery everything seemed ok. In regards to the alarm going off and the lights flashing, it seemed to me that it
was something to do with the keyfob as whenever I touched the key after turning the car off it would trigger the alarm, replacing the battery in the key helped but I would still get the random alarm
triggers but I no longer have to disconnect the battery overnight (although I wish I would have continued doing that).

Basically everything is related and I plan to check under the wheel well as rcmIndz mentioned. I will let you know what I find within the hour. Anyway I went to turn the car on 20 minutes ago and the battery reads 3.14 volts so something is draining the battery while the engine is off. Assuming the alarm is being triggered due to a parasitic draw (and the alarm module under the wheel well is not actually in need of repair) how do I trace down the fault? What is the easiest way? I have read that the battery should be exporting a certain very low amount of voltage when the car is at rest and turned off but I dont know the process as to how to control variables and track down the culprit, in other words I do not know enough about battery voltages and how much each component draws from the battery when the car is off if it should at all

Does anyone have experience with this? I am going to look at the alarm module now, i will post again shortly

kajtek1

20 minutes ago, but how long the car sit?
Discharging big battery down to 3v takes big draw and finding it takes some time.
Hook up amp meter to the battery and play with pulling the fuses.

efonz

Just an update if anyone was hoping for a solution to a similar problem. Unfortunately, I have no idea why the new battery drained overnight or what was going on with the alarm but ever since my last post the problem has not resurfaced and its been more than a week so I guess the E5 heard my gf complaining about wanting to go to the beach and good ol' benz knows i dislike the heat so he discharged himself and saved me once again. The details man the details, always the details.

arto_wa

Sorry to say, but it sounds like you have not solved the problem yet and it's going to bite you in the axx one of these days.

efonz

I agree, meant to imply that in my previous post.

rcmlndz

When the siren module went bad in my 2004 E500 it would act up randomly. Sometimes it would take a couple of weeks before it start to drain the car battery again.