Rear motor disabled

Rear motor disabled

My new Model 3 (2400 miles) died a few days ago.
I was leaving for work & I couldn't get the car to operate.
It displayed 2 errors:
1. Rear motor disabled (exit & re-enter car - may restore operation).
2. Car shutting down (pull over safely)

When pressing the brake the car would make a clunk & spinning noise in the rear
sort of like when a bad transmission switches gears.
The help desk tried to help out with no joy & eventually had to have the car towed.
It's at the service center awaiting a new rear motor & harness.
The good thing is that it happened while under warranty & I have a nice
Model S loaner.
The service department was very courteous & helpful. I sure hope this is
just an isolated issue.

crmedved | 9 april 2019

Interesting! I never thought there would be an actual use case for the dual motor redundancy they advertise. I assume you had a RWD?

That sucks though. Hope they fix it up soon!

Magic 8 Ball | 9 april 2019

There have been two use cases, I have read on this forum, of dual motor in "limp mode" when one motor went bad.

carabella | 9 april 2019

My model 3 is a dual motor long range

crmedved | 9 april 2019

Well, that's kind of disappointing. This is what they describe dual motor as:

"Tesla All-Wheel Drive has two independent motors. Unlike traditional all-wheel drive systems, these two motors digitally control torque to the front and rear wheels—for far better handling and traction control. Your car can drive on either motor, so you never need to worry about getting stuck on the road. If one motor stops working, you can safely continue to your destination with the second."

I guess that's not always true...?

carabella | 9 april 2019

You are correct -crmedved- that did not happen.
The car had the bug messages & a loud error horn/sound.
It never budged until the tow truck put it in tow mode to get it out of the garage.

Mikael13 | 9 april 2019

Interesting. That’s one the main reasons I purchased a dual motor (and the quicker 0-60). I was always afraid of getting stranded if the motor goes. That seems like false advertisement then. Would love to hear the findings @carabella. Btw, sorry that happened to you and with low miles too. I’ve only had my car for less than a month. Hope this doesn’t happen on a long drive down to SoCal

Magic 8 Ball | 9 april 2019

Jesus, not all failures are the same. There have been two cases reported of one motor going bad and the other getting the driver home.


SteveWin1 | 9 april 2019

"you NEVER need to worry about getting stuck on the road." Sounds like they need to adjust their wording. This isn't true if even one person has a single motor failure that prevents them from driving.

Magic 8 Ball | 9 april 2019

It is true of the "you" that are able to take advantage of the feature.

You might have a better argument if he said everyone.

njchillie | 9 april 2019

Apparently, carabella did have to worry. Sorry, carabella, but the “you” in that written description did not actually mean you.

lordmiller | 9 april 2019

I love Magic 8 Ball!! Cracks me up when someone says something idiotic and you crack 'em.

carabella | 9 april 2019

I think the rear motor would work if the front one went out but not the other way around as in my case?
I don't know that for a fact but if you operated on the front motor wouldn't that be a FWD which Tesla doesn't isnt?

carabella | 9 april 2019

Correction -
I think the rear motor would work if the front one went out but not the other way around (as in my case).
I don't know that for a fact but if you operated on the front motor wouldn't that be a FWD which Tesla isn't?

Mikael13 | 9 april 2019

@carabella - do give an update once you get your M3 back. Hope it’s nothing major

crmedved | 9 april 2019

I would expect reduced capacity, but I would have expected to be able to drive on the front monitor at highway-ish speeds. Maybe my expectations are a bit high. You should ask the SC why you couldn't drive it with one motor. I think lots of people would be interested in the explanation.

I expect my motor to outlast the car (obviously that doesn't always happen), so the redundancy wasn't really a selling point for me personally... but it is still interesting.

Jalinllc | 9 april 2019

My “guess” is that it has something to do with the actual failure mode detected in the motor / drive mechanism and if it is safe or even possible for the failed motor to free roll.

rxlawdude | 9 april 2019

With the AWD MS, a failure of the rear motor will disable the car, because the front motor is "daisy chained" from the rear motor.

A front motor failure, on the other hand, should allow "limp mode."

SteveWin1 | 9 april 2019

@rxlawdude, that would make sense.

But that would mean there is exactly zero benefit of having dual motor with respect to reliability. With either single motor or dual motor, you'd be at the mercy of your rear motor, right? So its still misleading to say that there is some benefit to having an extra motor up front, from a reliability standpoint.

rxlawdude | 9 april 2019

@SteveWin, I agree. After many years on the MS forum, I can't recall anyone having a rear motor failure that allowed them to drive on the front motor. There are some other MS vets here that might chime in if they've seen rear failure being recoverable.

CharleyBC | 9 april 2019

So, let's suppose for a moment that with a dead rear motor you COULD drive using only the front motor. How would that actually work? As the car is driving along under front wheel power, aren't the rear wheels spinning the rear motor? In effect the rear motor becomes a continuous brake. Unless there is a clutch or something that would let the wheels spin and leave the motor stationary. How would this work?

[At this point perpetual motion advocates can jump on this scenario to say that the regen from the spun rear motor is keeping the car charged so the front motor can go forever.]

carabella | 9 april 2019

I appreciate all the replies. I will post the final outcome once my car is repaired.

lbowroom | 9 april 2019

With the Model 3 it is possible for one motor to fail and still have limited drive capability. Possible doesn't mean that will happen in all failure modes. Like someone else mentioned, if a motor fails in a way that prevents it from turning, it can't be driven. Also, this isn't meant to serve for long term after the failure. Asking if the rear motor doesn't work if the car now categorized as front wheel drive and if that violates the description of a Tesla, you're blowing my mind.....

edhchoe | 9 april 2019

Maybe we need triple motors ...

Pepperidge | 9 april 2019

Since the rear PMSRM has magnets in the rotor, it generates high voltage when it turns and could cause more damage to the motor and/or inverter module.

kallian | 9 april 2019

Technically speaking since the front motor is induction (no perm magnets), then it can be limped with no power. It will not generate current while rotating. The rear motor is a permanent magnet motor that cannot be limped (cant get rid of magnetism as its permanent). This is because as the armature rotates, it will generate power, causing all kinds of weird issues when broken. (shorting/fire from massive amounts of energy acting as a generator)

So in short, dual motor/P if your front motor dies, you can limp your way home, if your rear motor dies, you cannot limp home. So there is redundancy depending on which motor dies.

Carl Thompson | 9 april 2019

Well, then, to me this seams obviously false:
"Your car can drive on either motor, so you _never_ need to worry about getting stuck on the road."

But @Magic 8 Ball says it's not in any way misleading so I must be wrong.

ken.lunde | 9 april 2019

The new Tesla Roadster has triple motors.

Mikael13 | 9 april 2019

Lol Carl

lbowroom | 9 april 2019

When I ordered the car I read that statement and laughed. I could visualize the marketing idiot who came up with that one. He's the one who also asked if they could claim it was all natural flavor.

jjgunn | 9 april 2019

What a weird thing to have happen.

Rear is for power & front is for range. But still surprised the car wouldn't continue. Interesting. Very very VERY rare situation. As M8B said only TWO reported on this forum.

Stuff happens.

ST70 | 10 april 2019

@edhchoe- YES! I need the Roadster now!

AWDTesla | 10 april 2019

On the boards I've read, I haven't read one instance of the rear motor falling and the front one getting the person home. Always resulted in a flat bed home for the model 3. I'm sure I've triggered a few fanbois now.

AWDTesla | 10 april 2019

@Carl Thompson funny heh, guy calls out every other thread as fUD but as soon as a thread fits his narrative, PRAISE TESLA! HALLELUJAH!


carabella | 12 april 2019

Hello everyone.
My dual motor Model 3 has been repaired.
The tech explained the following: It was a rear drive unit failure.
Tesla replaced the rear drive unit and sub-frame harness.
He explained that the vehicle is rendered inoperable because it automatically protects itself from internal damage such as internal binding & configuration failure.
If it had been the front motor you could limp on the rear.
He said it was not common (hit & miss) and a first for them (in Atlanta, GA).
Thanks for all the replies.

tom69302006 | 11 juni 2019

We were driving our brand new model 3 home from the dealership when we heard a thump and the rear motor became disabled. The message said it could still drive but that there would be reduced power. We were traveling on the interstate and my max speed and that point was 58 mph. Then the car began making a new loud sound and I became too nervous to continue driving. We exited the interstate ASAP and waited two hours for a tow truck to pick the car up to take back to the dealership.

beaver | 11 juni 2019

Thankfully it sounds like most of these motor (drive) failures have happened in the first few thousand miles. It must be terrifying. Hopefully at 30k I can rest easy. Good luck and stay safe

Cclcal | 11 juni 2019

Definitely not an isolated incident.

Our Single motor M3 died at 3000 miles.
Tesla put in new drive unit.
Diagnosis: rear drive unit failure. No cause given.
Car just came to a stop - from 65+mph to zero. Not coasting mind you, but more like low regen brake was on.
Not safe at all esp on highway. Luckily made it to shoulder just as car came to a stop.
Tesla didn't seem to concerned, just told me it's an easy replacement.
Im sure they will care when M3 comes to stop in the middle of highway and gets demolished by car coming up on it...

But 12K miles now, so far so good.

Magic 8 Ball | 12 juni 2019

@Cclacal At 60mph a TESLA Model 3 takes 133 feet to stop in a hard brake. In a hard regen slowdown the distance is longer, plenty of time to pull over to a safe stop.

Nothing lucky about you being able to pull over at all, everyone has the same "luck".

howard | 12 juni 2019

Magic 8 Ball, Nothing lucky about you being able to pull over at all, everyone has the same "luck".

Unless you are in a middle lane in peak rush hour traffic then one could not be so lucky.

I find it interesting that you have used an "everyone" statement. Do you know everyone and everyone's individual circumstances?

Magic 8 Ball | 12 juni 2019

@howard In this case, I do, because the stopping distance is a physical parameter of the vehicle. Even if you are stuck in a middle lane the stopping distance/time, without braking (I.E. regen available at 65 mph) is more than adequate for traffic to avoid colliding with you.

There are so many stories of sky is falling exaggeration here it is ridiculous.

Magic 8 Ball | 12 juni 2019

@howard Did you happen to notice I put "luck" in quotes? I usually do that sort of thing to mock the use of the word, FYI.

jjgunn | 12 juni 2019

Re-reading this thread.

Interesting that the 2 motors are linked like master (rear) slave (front).

It's definitely a rare occurrence but I wonder if Tesla will take a look at this so either motor can operate the vehicle. Instead of a hard & fast Master/Slave, they should be easily able to use software & make it more like Active/StandBy where the front motor takes over as master if the master fails.

howard | 12 juni 2019

M8B, There are so many senseless defenses of Tesla and one's own made remarks here it is ridiculous. Lost count of how many others you have flames for making similar statements.

I have seen stop and go traffic where a car traveling behind a fast stopping car in front of it quickly moves to an adjacent lane and the fast traveling car behind that car cannot do the same and hits the car that was quickly uncovered in a stopped condition. A few others involve cars that have stopped in snowing conditions here in CO and get plowed by the car behind that can't stop.

Your constant defenses are not all knowing and..... I know you'll never believe that, right?

jimglas | 12 juni 2019

Looks like another Howard vs M8B flame war is about to start

howard | 12 juni 2019

Magic 8 Ball | June 12, 2019
@howard Did you happen to notice I put "luck" in quotes? I usually do that sort of thing to mock the use of the word, FYI.

Good defensive cover, again.

Magic 8 Ball | 12 juni 2019

@howard Actually there are those that have gotten me to change my mind about my opinion, it is easy to teach me with facts I can confirm.

In a rear end collision you describe no one can control the actions of a tailgater (person that follows too close). If someone has to do an erratic avoidance maneuver they were not paying attention. I have yet to find a car that will avoid drivers that are not paying attention.

You ridiculous attempts to lay blame on the auto instead of the driver is just more selfish entitlement being displayed.

Magic 8 Ball | 12 juni 2019

Did you miss the kcheng war last night, he was on fire until the drugs wore off.

Magic 8 Ball | 12 juni 2019

@howard writes: "Good defensive cover, again"

Try to keep up, I cannot edit my posts so I was playing offense and you are not even in the game.

Cclcal | 12 juni 2019

@magic8ball I consider it lucky because if the highway was full of cars going 65+mph then a sudden loss of forward propulsion would definitely cause some concern and possibly a pile up if the other drivers are driving full speed and/or slightly distracted and if we were unable to make it to shoulder.

Magic 8 Ball | 12 juni 2019

Oh I do love those "IFS". Nobody is saying it is normal but all other brands have occasional failure that can cause issues. Drive safely and leave plenty of room.

If my aunt had balls she would be my uncle.