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P85D Front Motor Died

I felt some stuttering yesterday as the car regen braked. Then another stutter and red lights flashed with service warnings about the front motor. I had no power and drifted to the side of the road. I had to get out of the car for it to shut off and then restart, but the front engine came back alive and I drove the last half-mile home. This morning on the way to work, the same stuttering on regen braking and then front motor failure, but this time it was only white (as opposed to red) warning, and it let me drive after it automatically shut off the front, and carried on with just the rear, for the last mile to work.

Tesla picked it up this morning and just called to say it would likely be several days while they ordered a new front motor. :(

I only had about 3,800 miles on the car so far.

Has this happened to anyone else? Should I be worried about any permanent damage to other parts of the car that Tesla might not replace in this case?

Thanks.
 
I have a 70D and my rear motor went out after 2000 miles. Unfortunately my car wouldn't even budge after it went bad. After a tow however and a motor swap (which they had on the shelf) I was back to normal in no time. Other than an unusually long wait for a tow the experience was pretty painless.
 

ecarfan

Well-Known Member
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Sep 21, 2013
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West Vancouver, British Columbia
Interesting. I thought the P85D would allow you to limp along on one motor?
I read the OP to say that in both instances he could drive with just one motor.
However the post by @Rule_of_72 says he could not drive on just the front motor after his rear motor failed.
I have a 70D and my rear motor went out after 2000 miles. Unfortunately my car wouldn't even budge after it went bad. After a tow however and a motor swap (which they had on the shelf) I was back to normal in no time.
Did you ask Tesla why your car was unable to move on the front motor only?
 
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My front motor went out at <2000 miles, but the only indication of a problem was messages on the display (front motor disabled, power reduced). There was no stutter or other indication that a problem existed. Reduced power down to 470 Hp in the rear wasn't a big problem. :) Service center fixed it in a few days, said it was a failed temp sensor, so the car thought it was overheating.
 

ecarfan

Well-Known Member
Moderator
Sep 21, 2013
19,505
14,528
West Vancouver, British Columbia
It appears that a rear motor failure is catastrophic but not the front. With a functional rear motor, it'd be no different from the RWD Model S.
I had thought that a rear motor failure in a Dual Motor car would not necessarily prevent the car from moving, and that it could move on the front motor alone. While this thread provides evidence against that hypothesis, I would not assume that in every instance of rear motor failure the car will be unable to move, as there are complexities to the system that those of us who are not Tesla engineers are likely unable to fully appreciate.
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
Well, the accelerator pedal is hooked to the rear motor only, and apparently it sends the torque commands to the front motor via the CAN bus. So if the rear motor fails such that the inverter logic is offline, the car is dead.
 
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ggr

Expert in Dunning-Kruger Effect!
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Mar 24, 2011
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San Diego, CA
Well, the accelerator pedal is hooked to the rear motor only, and apparently it sends the torque commands to the front motor via the CAN bus. So if the rear motor fails such that the inverter logic is offline, the car is dead.

What does "hooked to" mean? My understanding (possibly wrong) is that the accelerator pedal is really only connected to a spring-loaded position sensor, which sends the position to the power module via CANbus. The power module then figures out what power is needed in both motors, and sends appropriate commands to the front motor. Since it's integrated with the rear motor, I guess it just controls it directly.
 

Ingineer

Electrical Engineer
Aug 8, 2012
1,507
3,712
No, the pedal sends 2 analog voltages to the rear inverter (aka "power module") and that inverter generates the CAN frames that are sent to the front motor, so if the rear inverter is non-functional, then the front motor can't get CAN frames.

- - - Updated - - -

I thought Elon had said that if "one" of the motors failed the "other" could still be used... Could they adjust this with software such that that in the event of a rear motor failure, the car can be driven with just the front motor?

Yes if "One" of the motors that fails is the front motor, and the other motor (rear) is still good, then the car can still drive.
 
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brianman

Burrito Founder
Nov 10, 2011
17,615
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Yes if "One" of the motors that fails is the front motor, and the other motor (rear) is still good, then the car can still drive.
Point of clarification:
I can't speak to the rear motor failures, but in the case of front motor "failure" it depends. Some front motor failures are compatible with the car being allowed to "limp" along with just the rear drive unit, some aren't.
 

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