Ayyildiz

Back in march my car randomly had the siren go off while i was parked at work and i didnt think much of it, it continuously got worse so I replaced the alarm siren itself but that didnt fix the problem.

Ive replace
the kef fob battery,
the cars battery (which was undersized from the previous owner),
alternator and voltage regulator,
hood latch cable,
the trunk actuator switch,
door jam switches
due to think it was an issue with the alarm system but that hasn't fixed anything

from the command screen while the car is off the battery voltage drops down to 10.6V but starts up fine with no issues and it idles around 13.1V - 13.5 V, Ive checked continuity on all fuses and none of them are blown but i havent checked amperage and thats what im leaning toward next.

Can someone point me in the right direction?

BlownV8

Do you have an E or a CL?

Ayyildiz

both, I posted in a 210 forum bc I have a 210

BlownV8

You may want to update your profile as it just lists the CL.

Do a test on each fuse to see what is drawing power when it isn't in use. My old 210 was kept on the battery maintainer as I never drove it. It's a very common issue but I never looked into since when I did drive frequently it was never an issue. How often do you drive your E55?

Ayyildiz

Should I do am amperage test on each fuse with the key not in the ignition or in position 2? And I drive it daily

BlownV8

Yes, that's what I would do. Is it running your battery down even when it's your daily? Are you having to jump start? How old is the battery?

Ayyildiz

I’ve never had to jump start it, it’s never had an issue starting up, and I’ve never died on me after parking it for an extended period of time.

I just bought a new battery earlier this month due to the battery being nearly 4 years old and I found out the battery the previous owner put into to was a 70Ah battery but the oem battery is rated for 100 Ah.

The thing that makes me think it’s a parasitic draw is the command screen while using the rest menu option 24, drops to 10.8v after parking it and then putting the key in position 2 to check it. But like i said earlier it’s never died that’s what’s throwing me off, im not sure if its the security system either.

BlownV8

4 years for an undersized battery is good. I wouldn't spend much time worrying about it.

Ayyildiz

another thing is my car alarm going off, I’ve replaced the siren itself, the key fob battery, trunk and hood switch’s only thing I’m thinking is after replacing the alternator driving it a longer distance to properly charge it up

RKP Waco

The PSU pump has a bad habit of failing and causing this problem. It’s the pump next to the battery that controls the door locks.

Ayyildiz

I’m not having any locking issues, everything locks and unlocks properly, only issue I had recently was the trunk not locking occasionally.

I replaced the trunk lock actuator micro switch ( 208 820 10 10) that sends the signal to open the solenoid valve to send the air to the trunk lock and it’s worked again since with no issues

What are clear signs of a failing pump that I haven’t listed?

RKP Waco

The pump can work just fine and still draw power. Unplug it and see what happens.

Ayyildiz

Okay, I thought you were referring to it on a mechanical standpoint. Is there a fuse for it or a connector that plugs in. I’ve looked at the fuse diagram but I don’t recall a fuse for it, I’ll look into it. Thanks.

RKP Waco

Unplug it and then check your battery the next day. Unless you know how to hook up an amp meter to it to see if it’s drawing power while the cars turned off.