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Rear Drive Motor Fault causing 12V Battery to discharge

DarkNightP3D

Member
Jan 10, 2020
141
178
Raleigh, NC, USA
We got 2 Model Y LR AWDs in mid-December. This morning we went to open the door of one of them and nothing would happen. The app was perpetually trying to connect. The screen would not illuminate. Key card did nothing. So, I call Tesla Support and they say the 12V battery is discharged and needs to be replaced. The girl acted like we should’ve known... we never got any warnings on the app or car.

Thankfully they were able to get mobile service to us within a couple hours. He replaced the 12V battery and starts doing diagnostics and discovers a stored fault in the rear drive unit. He said it’s an “isolation” fault causing the contactor to never disconnect leading to perpetual battery drain. It will either need a new rear drive motor or possibly a “card” in the drive motor could be replaced. With only 800 miles on the odometer it’s a bit disappointing that it now has to be towed 170 miles away for a repair, but what do you do. Things happen with any car, I’m just hoping it’s not signs of things to come.

Both are late-November production. The ranger said he’s never seen this exact issue, but supposedly Tesla updated the motor on the new 3/Ys with these replaceable cards (not sure if he is talking about a computer chip in the motor or what) but he said usually that’s the point of failure for the motors. I guess before they were replacing entire motors when just this one card could be replaced. So now in most cases it’s just a part swap instead of entire new motor.

Has anyone else experienced this issue? I searched for Model Y rear drive motor issues and didn’t really see a trend of this being a documented issue.
 

Watts_Up

Active Member
Mar 4, 2019
3,629
2,451
In a galaxy far, far away
Sorry for your issue on a brand new car, but the good news is that the mobile service was able to diagnostic the problem.

I don't know if this was the disconnect which was mentioned, but after about 5 minutes after locking the car,
the car goes in sleep mode and there is a noticeable 'Dong' noise every time the car goes to sleep or weak up.

Otherwise there is real way to know if the car is asleep.

I put on top of my console, a little wireless charger connected to the auxiliary 12 V plug.
The wireless charger has a red LED when connected, which turns blue when charging a phone,
and the LED is off when there is no power.

So from the outside I can see if the car 12v auxiliary power is on or off.

Also if I choose to keep the Sentry on, the red LED stays on, which is a simple way to check the Sentry status.​

I would also recommend installing a 12 V battery monitor which can be access remotely using a Bluetooth app from your phone.

The app displays a continuous voltage voltage of the battery.

I would recommend using additional bolts when attaching the device to the battery as the screws are long enough
so there will be no risk to disconnect the battery wires from the car when connecting the device.​

Typically if you are not driving, the 12 V battery slowly get discharge and when reaching about 12.50 V
(after 2 days in my personal case) the inboard charger get activated and charge the 12 V battery at 14 V during 2 hours.
At the end of charging, the battery returns to a steady 13 V and starts again slowly discharging until reaching 12.50 V.​

This could be a good way to determine if there is any thing wrong with the 12 V battery
and in particular if the battery cannot keep the charge and then needs to be replaced.​
 

DarkNightP3D

Member
Jan 10, 2020
141
178
Raleigh, NC, USA
Sorry for your issue on a brand new car, but the good news is that the mobile service was able to diagnostic the problem.

I don't know if this was the disconnect which was mentioned, but after about 5 minutes after locking the car,
the car goes in sleep mode and there is a noticeable 'Dong' noise every time the car goes to sleep or weak up.

Otherwise there is real way to know if the car is asleep.

I put on top of my console, a little wireless charger connected to the auxiliary 12 V plug.
The wireless charger has a red LED when connected, which turns blue when charging a phone,
and the LED is off when there is no power.

So from the outside I can see if the car 12v auxiliary power is on or off.

Also if I choose to keep the Sentry on, the red LED stays on, which is a simple way to check the Sentry status.​

I would also recommend installing a 12 V battery monitor which can be access remotely using a Bluetooth app from your phone.

The app displays a continuous voltage voltage of the battery.

I would recommend using additional bolts when attaching the device to the battery as the screws are long enough
so there will be no risk to disconnect the battery wires from the car when connecting the device.​

Typically if you are not driving, the 12 V battery slowly get discharge and when reaching about 12.50 V
(after 2 days in my personal case) the inboard charger get activated and charge the 12 V battery at 14 V during 2 hours.
At the end of charging, the battery returns to a steady 13 V and starts again slowly discharging until reaching 12.50 V.​

This could be a good way to determine if there is any thing wrong with the 12 V battery
and in particular if the battery cannot keep the charge and then needs to be replaced.​
There is an isolation fault with the rear drive motor according to the mobile tech. I’m really about to lose it though with my local service center. This entire thing has been ridiculous.

first; it was supposed to be picked up last Friday afternoon and towed to the Raleigh, NC service center. Nobody showed up. I called Saturday morning and they had no record of a tow request made by the mobile tech. So, roadside service set up a tow. The tow truck guy gets there at 7PM Saturday night. As opposed to what I was told by the mobile tech the day before, the car was NOT in tow mode ready to go. It was locked up and wouldn’t move. The 12V battery had been disconnected which I told the tow truck driver. He didn’t know how to get to it... so I had to tell him how to open the frunk by connecting power to the wires that you pull out, then pull off the cover around the frunk and get to the 12V battery. Finally after being there an hour, he got it to power on to put it into tow mode.

Monday morning I called Tesla to make sure they know the car was dropped off over the weekend. I get no reply. I call back 4 times that day and nobody ever picks up or returns my voicemail. Tuesday morning I call again several times and no response. So I finally drive to the service center and see the car still sitting exactly where it had been when the tow truck driver left it Saturday night.

I go inside and talk to the guy at the desk who has no record that the car was brought there... so now we are on like internal communication failure 3. It really is baffling they could have managed the repair of a completely non-driveable 2-week old car so poorly. The service guy said they would call me that afternoon to tell me what the issue is. Well, nobody calls. So yesterday I called 3-4 times and finally go through and he says “we will try to get it diagnosed this afternoon or tomorrow morning”.

It’s THURSDAY and the car has been sitting completely dead for 6 days... 5 days at the service center without apparently being touched. I’m getting ready to drive back to the service center because it’s now 10:30AM and I’ve yet to hear what’s wrong. The guy yesterday said it may need a new battery pack or may need a new rear motor. They weren’t sure. The mobile tech told me it was a simple “card” that needed to be replaced in the rear drive unit. I’m sorry, but this is just plain incompetence.
 
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xyskis

Member
Jan 10, 2021
33
24
Portland
There is an isolation fault with the rear drive motor according to the mobile tech. I’m really about to lose it though with my local service center. This entire thing has been ridiculous.

first; it was supposed to be picked up last Friday afternoon and towed to the Raleigh, NC service center. Nobody showed up. I called Saturday morning and they had no record of a tow request made by the mobile tech. So, roadside service set up a tow. The tow truck guy gets there at 7PM Saturday night. As opposed to what I was told by the mobile tech the day before, the car was NOT in tow mode ready to go. It was locked up and wouldn’t move. The 12V battery had been disconnected which I told the tow truck driver. He didn’t know how to get to it... so I had to tell him how to open the frunk by connecting power to the wires that you pull out, then pull off the cover around the frunk and get to the 12V battery. Finally after being there an hour, he got it to power on to put it into tow mode.

Monday morning I called Tesla to make sure they know the car was dropped off over the weekend. I get no reply. I call back 4 times that day and nobody ever picks up or returns my voicemail. Tuesday morning I call again several times and no response. So I finally drive to the service center and see the car still sitting exactly where it had been when the tow truck driver left it Saturday night.

I go inside and talk to the guy at the desk who has no record that the car was brought there... so now we are on like internal communication failure 3. It really is baffling they could have managed the repair of a completely non-driveable 2-week old car so poorly. The service guy said they would call me that afternoon to tell me what the issue is. Well, nobody calls. So yesterday I called 3-4 times and finally go through and he says “we will try to get it diagnosed this afternoon or tomorrow morning”.

It’s THURSDAY and the car has been sitting completely dead for 6 days... 5 days at the service center without apparently being touched. I’m getting ready to drive back to the service center because it’s now 10:30AM and I’ve yet to hear what’s wrong. The guy yesterday said it may need a new battery pack or may need a new rear motor. They weren’t sure. The mobile tech told me it was a simple “card” that needed to be replaced in the rear drive unit. I’m sorry, but this is just plain incompetence.

This is terrible! I’m so sorry! Please keep us updated on the progress and outcome.
 

DarkNightP3D

Member
Jan 10, 2020
141
178
Raleigh, NC, USA
This is terrible! I’m so sorry! Please keep us updated on the progress and outcome.
So I just drove to the service center (again) and the car is literally sitting there in the SAME exact spot but the driver side door is wide open and the window down. Nobody came over to the car the 10 minutes I sat there and watched. So I don’t know what the hell they are doing. Because it is undriveable I guess they can’t move it around? I would imagine they’d have dollies or something to move dead cars. Maybe not?
 

bozer

Member
Jul 13, 2020
101
41
NJ
I just had something similar happen as well. I wonder if its recent update? I went out to my car, was able to get in, but the screen was totally dead and I couldn't get the car on. App would not connect at all either. I ended up rebooting by pressing the two buttons on the wheel in, which fixed it. I was worried my car was bricked. Never happened before. AWD Non performance Y
 

DarkNightP3D

Member
Jan 10, 2020
141
178
Raleigh, NC, USA
I just had something similar happen as well. I wonder if its recent update? I went out to my car, was able to get in, but the screen was totally dead and I couldn't get the car on. App would not connect at all either. I ended up rebooting by pressing the two buttons on the wheel in, which fixed it. I was worried my car was bricked. Never happened before. AWD Non performance Y


Our car was literally completely dead to the point you couldn’t open the door the app didn’t work and you out of the screened in a while. I just got a message from Tesla that they diagnosed this as a heat pump high voltage harness and that part is out of stock but they’ve “expedited a replacement” but have no ETC on repair.
 

seniorcitizen

Member
Oct 9, 2020
212
119
Maple Grove
I am sorry about your experience. Quality issues coupled with poor service are a disaster.
Mobile tech coming in a few hours to diagnose the problem was great. Rest of the experience was beyond belief.
In addition to selling as many cars as they can I hope they are also investing in training/staffing of their service centers.
 
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Reactions: CaptainX

DarkNightP3D

Member
Jan 10, 2020
141
178
Raleigh, NC, USA
I am sorry about your experience. Quality issues coupled with poor service are a disaster.
Mobile tech coming in a few hours to diagnose the problem was great. Rest of the experience was beyond belief.
In addition to selling as many cars as they can I hope they are also investing in training/staffing of their service centers.
What’s even more unbelievable is that it’s still sitting there dead. Now the other Y we got in December is having autopilot issues. It’s giving frequent warnings that Autopilot safety features are unavailable. I called customer support and was told the front cameras are offline and the right pillar camera isn’t calibrated. This is really not giving Tesla a good look to my family members, one who can’t drive his car all (the dead Y) and the other who can’t use cruise control or depend on any of the safety features to work because of camera failures.
 

DarkNightP3D

Member
Jan 10, 2020
141
178
Raleigh, NC, USA
Similar issue happened to us.

Our new MYP towed to service...
So I just got off the phone with Tesla. They’re not expecting the wiring harness to even come in now until 1/25... the car has been undriveable since 1/6. So we will be lucky if we get the car back within 3 WEEKS for a simple wiring harness replacement. If it goes one week longer it will qualify for manufacturer buyback under NC lemon law.
 

MutleyCrew

New Member
Apr 29, 2021
3
8
Northern VA
We have a Tesla Y, Dual Motor. Took delivery at the end of 2020. 1,800 miles on it and alerts pop up on the dash during a road trip. Lose power to accelerate and I coast it to the shoulder. Comes to a shuddering stop that felt like air brakes and then doesnt shift out of Park. Attempt multiple reboots, nothing works. Call Tesla roadside assistance and get a tow 2 hours later.

Towed to the Richmond, VA Telsa dealership. Service shop not open (Sunday), and only Sales are on site. Tell me they dont have a loaner because Service dept. isnt open?! $70k car with 1800 miles on it that broke down, stuck hours from home and told to "go get a rental". Was not happy about that experience, felt let down. Ended up calling roadside assistance back and having them set up a rental for me, on their dime.

Rear drive unit is not communicating with the rest of the vehicle and needs to be replaced. Not a good start...
 
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Reactions: srlawren

DanDi58

Active Member
Jun 22, 2020
1,149
842
Dayton NJ
We have a Tesla Y, Dual Motor. Took delivery at the end of 2020. 1,800 miles on it and alerts pop up on the dash during a road trip. Lose power to accelerate and I coast it to the shoulder. Comes to a shuddering stop that felt like air brakes and then doesnt shift out of Park. Attempt multiple reboots, nothing works. Call Tesla roadside assistance and get a tow 2 hours later.

Towed to the Richmond, VA Telsa dealership. Service shop not open (Sunday), and only Sales are on site. Tell me they dont have a loaner because Service dept. isnt open?! $70k car with 1800 miles on it that broke down, stuck hours from home and told to "go get a rental". Was not happy about that experience, felt let down. Ended up calling roadside assistance back and having them set up a rental for me, on their dime.

Rear drive unit is not communicating with the rest of the vehicle and needs to be replaced. Not a good start...
That stinks for sure. But if you had, say, an Audi or M-B and had it towed to the dealer on a Sunday, would you expect the service department to be open and arrange for a loaner for you? The fact that Roadside Assistance was able to get a paid-for rental for you is great. There are enough issues with Tesla overall; I don't think we need to put larger expectations on them than we would another expensive brand.
 

everydaychris

Member
Feb 10, 2020
621
315
CA
Sorry for your issue on a brand new car, but the good news is that the mobile service was able to diagnostic the problem.

I don't know if this was the disconnect which was mentioned, but after about 5 minutes after locking the car,
the car goes in sleep mode and there is a noticeable 'Dong' noise every time the car goes to sleep or weak up.

Otherwise there is real way to know if the car is asleep.

I put on top of my console, a little wireless charger connected to the auxiliary 12 V plug.
The wireless charger has a red LED when connected, which turns blue when charging a phone,​
and the LED is off when there is no power.​
So from the outside I can see if the car 12v auxiliary power is on or off.​
Also if I choose to keep the Sentry on, the red LED stays on, which is a simple way to check the Sentry status.​

I would also recommend installing a 12 V battery monitor which can be access remotely using a Bluetooth app from your phone.

The app displays a continuous voltage voltage of the battery.

I would recommend using additional bolts when attaching the device to the battery as the screws are long enough​
so there will be no risk to disconnect the battery wires from the car when connecting the device.​

Typically if you are not driving, the 12 V battery slowly get discharge and when reaching about 12.50 V
(after 2 days in my personal case) the inboard charger get activated and charge the 12 V battery at 14 V during 2 hours.​
At the end of charging, the battery returns to a steady 13 V and starts again slowly discharging until reaching 12.50 V.​

This could be a good way to determine if there is any thing wrong with the 12 V battery​
and in particular if the battery cannot keep the charge and then needs to be replaced.​
Most useful post
I have a radar detector with a voltage reading and was always confused why it would drop to 12.5 and then jump back to 14 after the car going to sleep for the night. Was confused because the car was never on. Cool how teslas are different
 

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