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Bizarre System Power Failure

FrozenCanuck

Member
Feb 24, 2014
179
36
Port Perry, Ontario
My model year 2014 Model S just had a weird failure today. I dropped my kid off at school and went to the gym as usual. I returned to the car after my workout, but the screens were blank, and I thought it was just one of those occasional system reboots that happen to us all. No big deal right? Takes 20 seconds and you're driving again.

Nope.

The screens came up and I got a warning message that the system was shutting down and a variety of related messages, that kept appearing when I tried to put the car in gear.

I called Roadside Assistance and told the what was happening. The nice lady pulled up the logs and said my car was reporting a 12V battery problem. I thought that was weird because there were NO warnings ahead of time, and I have experienced a failing 12V battery once before. Normal warning, service changed out the battery ... all good.

I just left my car at the gym and walked home. I researched things and realized I could boost the 12V battery myself, so I got the equipment together and went back to my car about 2 hours later.

NO ISSUE - the car just started as if nothing was ever wrong. No error messages, and I did NOTHING. I did not boost the battery.

Anyone have any idea what that might have been?

Side issues, perhaps, and perhaps related issues ... mobile service came to fix my door handle recently and could not repair it. But in the process of the repair, Fuse #40 (rear door controller power) blew. I had to diagnose this problem myself and let the ranger know by text message. He came back, fixed the fuse issue, tried again on the door handle and still couldn't fix it because it might have been a cable assembly issue in the door itself.

I started to wonder if a broken cable assembly could cause the 12V power to go down intermittently.

Thoughts?
 

N..8

Member
Dec 20, 2017
202
150
Sanford, NC
Sounds like the 12v battery had a low SOC on it and the HV battery pack took a bit to charge it back up. I would have thought that if the car powered up that the DC/DC would keep it going even with a low 12v but who knows.
 

FrozenCanuck

Member
Feb 24, 2014
179
36
Port Perry, Ontario
Sounds like the 12v battery had a low SOC on it and the HV battery pack took a bit to charge it back up. I would have thought that if the car powered up that the DC/DC would keep it going even with a low 12v but who knows.

Yeah I was thinking the same, but I’d been driving all over with no 12V warnings and then just BOOM, out of the blue car won’t start .... and 2 hours later it’s fine again. Really weird. Hard to explain. I’ll report back when Tesla diagnoses this.
 

FrozenCanuck

Member
Feb 24, 2014
179
36
Port Perry, Ontario
One more piece of evidence I just thought of: The other night (one or two days before the power shutdown incident), my car failed to install a software update that was available. I have never had a s/w update fail before. I just read a thread about how this update is gated by the 12V system - if low voltage is detected, the car rejects the update.

So that piece of evidence leads me to believe it was indeed a 12V issue ... but unfortunately it does nothing to explain why the issue suddenly disappeared after a couple of hours.
 

Electric700

Active Member
May 21, 2013
1,706
368
Florida, United States
One more piece of evidence I just thought of: The other night (one or two days before the power shutdown incident), my car failed to install a software update that was available. I have never had a s/w update fail before. I just read a thread about how this update is gated by the 12V system - if low voltage is detected, the car rejects the update.

So that piece of evidence leads me to believe it was indeed a 12V issue ... but unfortunately it does nothing to explain why the issue suddenly disappeared after a couple of hours.

The software update download could have been draining the 12 V, but I would expect the car to automatically connect the main battery to charge the 12 V when needed. You may want to have the 12 V tested, plus enable Energy Saving and leave Always connected off. The app might take slightly longer to connect.
 

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