Alarm goes off randomly
 

Soo..

Reached the end of my diagnostics skills on this one.
The alarm randomly goes off for no discernible reason on my 2000 S.
Also. Sometimes it single beeps when you lock it. Sometimes it does not.

Both door latches are new, the ignition switch is new.
I've verified that both trunk and frunk switches reliably turn on and off the lights in the compartments by putting a camera in there and opening/closing them.
Windows drop when you pull door handles and go back up when released.
Limit switches for roof registers full travel in either direction as well.

The alarm module is bone dry as is the compartment that it sits in.
I even removed the drivers seat to ensure that it didn't look like it had been wet at some point.
Found no tell tale signs.

Hooked up Durametric to see if any fault codes were stored in either of the alarm modules.
Both came up clean but maybe I'm holding it wrong.

Checked power and found that the battery was about a volt down from nominal (11.44) so took it to the local parts store to have it checked out.
They said battery was at 75% charge but otherwise checked out fine.
They also checked the alternator and came back with a failing voltage regulator.

Bought a new voltage regulator from PelicanParts and replaced it (along with the belt since I was already there).

Still same issue. Sometimes it'll sit for days. Sometimes it'll be minutes after you lock it.

Nothing in the logs that i can pull with the Durametric and nothing more that i can think of.
It's been about 2 weeks now.

The last few days a new issue has popped up.
Passenger side door doesn't unlock when you pull either inside or outside handle.
Or when you push the central locking button on the dash.
It only unlocks when drivers side door is unlocked, either by opening it from the inside or by unlocking it using keyfob or key.

I'm unsure if these two issues are related and how to proceed.

Any help and/or suggestions would be greatly appreciated.

1st, your battery is telling you something. Why is it at 75% charge? I would replace it

If that doesn't solve the issue then everything you are having issues with is classic signs of an immobilizer issue. You could send it, dme & keys off to ecu dr for testing & fixing & repair or look for a used immobilizer, dme & keys...or have dealer put a brand new one in & program it.

As to your battery showing 75% charge.
Failing voltage regulator could have been the cause.

I would put it on a charger then when charged take it in and have it "load tested"
A battery can show full voltage and still be shot.
That is where "load testing" comes in.
Charge level is not always an indication of a good or bad battery.

That's what I was worried would be the issue.

I actually bought their waterproof box and was going to fit it when it started acting up.
So for now it's sitting on my table.

Figured there wouldn't be any point in waterproofing a dud part.

As for the battery I chalked that one up to the voltage regulator.
Battery is under 2 years old.

Gonna take it back to the autoparts store this weekend to verify that replacing the voltage regulator corrected that issue.

But yeah. My fear was that this had all the tell tale signs of failing electronics.
Especially the fact that no codes are logged on fault.

Is there anything else that this could be before i take the plunge and send it all off for repair ?

@blue They load tested it at the parts store.
Battery passed at 860CCA.

My only concern is that voltage spikes from the failing voltage regulator could have fried something.

It could have harmed the battery, doubt it would do anything else.

In all honesty, batteries are just crap now. Have been for the past 10 years. If you get 1 year out one I think you are doing good. Anything more and it's a win which brings up a side note. The only difference in a 3 year batter vs 5 year, is the Price & Warranty. Otherwise it is the exact same battery. You just pay more for the warranty.

My opinion is that batteries are just being recycled too much. A battery today could be made from one that was already recycled 2 or more times so the quality is going go to down. Grab a battery from 30+ years ago, put a charge on it and I bet it would last longer then anything brand new today.

If the battery holds voltage when fully charged and passes a load test.
Then the battery is fine.

Resurrecting this thread. I am having similar issues and wondering if the OP ever figured it out.

I had a random alarm and traced it back to whether I had the windshield sun shield protector up or not. I think it was triggering the indoor movement detector, so if I ever have it up I just double click the lock button to deactivate the interior movement detection. This results in a single beep.

If the battery doesn’t end up fixing it, get a new alarm horn and replace that. It is a very common reason for frequent alarm activations, and the single chirp. It’s also inexpensive and super easy DIY. You can get the part from eBay, pelican parts, or a lot of other sources (including Porsche dealers online) for as low as $23.

I’m a professional pilot, and I used to often drove my car to work, where I would leave it parked at the FBO (private terminal) for a week at a time (covered, of course). They started calling me the “Car Alarm Guy” because the alarm was going off all the time. I started having to leave it unlocked under the cover. A little research and then replacing the alarm horn immediately fixed the problem.