New Subaru-installed battery dead after three days

[SFWharfRat]

Hi All. Need help determining what could possibly be wrong with my 2017 Forester.

The trouble started when I went out to my car about a month and a half ago, and it was soaking wet inside with mold. Back up to September, when I had a new windshield installed by a national windshield replacement shop. I hadn’t been driving that vehicle much, so it wasn’t until during the rainy season that I realized that the windshield was badly installed and was leaking. Note that the car was perfect before this. When the tow truck came to pick up my car, the battery was completely dead. It was towed back to the windshield replacement shop, who correctly installed the windshield, and they paid out-of-pocket $1200 to have my carpets replaced and the front interior of the car detailed. About a week ago I went out to my car, and the battery was dead again. So I jump-started the car and took it to the Subaru dealer and had a new battery put in. Today I went to pick up my husband from the hospital after surgery, and my battery is dead. I called the manager of the windshield shop who was so nice to me, and said I was concerned that there was a correlation, and that maybe my electronics got screwed up. He said it could be a myriad of things including my alternator. Deep in the back of my mind, I feel like the battery problems started with water leaking into my car from the top of the windshield. I could be wrong, because one may not have anything to do with the other, but I find it extremely coincidental that I seem to be having battery problems now. Does anybody here with mechanical knowledge know if the windshield leaking into my car for weeks could have gotten into the electrical system through the dashboard?

 

[Ecmbuster]

The wiring harness and or one or more internal components likely have some type of parasitic draw.
A professional technician that uses an AMP clamp on the negative cable, can measure the parasite.
With that test, each individual fuse (in parallel) or connection can be measured in the .mV scale to narrow the parasite to one or more circuits.
With the windshield leaking for weeks - Yes that shop is at fault and generally the connections close to the leak will indicate green oxidized connections. Make sure many photos are captured with the tests to prove the parasite.
The parasite is repairable.

 

[SFWharfRat]

This is all technical jargon which is exactly what I’m looking for. So I’m guessing that I need to go to my local Subaru service for said professional technician. May I ask your expertise level in case I’m asked who gave me the advice? Thanks again. I appreciate it.

 

[SFWharfRat]

I also just found this:

“Windshield leaking can also contribute to electrical failures. For instance, if a windshield leak reaches your car's sensors, it can cause these sensors to malfunction. In this scenario, you'll need to replace the sensors to ensure that your vehicle runs properly once again.”

 

[Ecmbuster]

Any smart independent Technician or Subaru Technician that understands how to measure a "parasite" can solve the constant "dead battery" issue.
That Technician will scan and save all recorded network faults as a primary guide saving all those steps.
The Technician will also photograph the parasitic amperage draw and what circuit or component, that is creating the parasitic draw.
(similar to keeping the lights on all day with no indication)
That becomes the proof for you.

What you found has truth to the statement but prefer to test and clean/replace/repair the defect(s).

 

[SFWharfRat]

Last question- Does the computer in my car log time stamps of mechanical failures? (Might be a dumb question.)

 

[Ecmbuster]

Depends on the controller (computer) and what it's capable of logging. Most controllers will record power supply errors/faults. An example set of faults:
https://www.autonationsubaruwest.com/service/obd-ii-trouble-codes.htm

One simple tool to use with a smartphone will test the battery voltage, alternator charging voltage and starting voltage.
As an example:
https://www.amazon.ca/Bluetooth-Battery-Monitor-Voltage-Wireless/dp/B074ZCM6YC