LDU won't spin. No errors. [SOLVED]

[nubster]

I'm having trouble getting an LDU to spin.

It's in Run mode and set to Forward direction, but when I apply throttle, nothing happens. I’ve calibrated the throttle, and when I plot it, it maps smoothly to the throttle angle. However, the current remains at 0, and the voltage remains relatively constant. There's no movement or noise from the DU when I apply throttle.

I've tried both LDU parameter sets from the parameter database, but I got the same result. I only changed potmin, udcmin, and udcsw. I measure 60.84V at the DC bus bars, but the web interface is reporting udc of 77.34V. I've tried three boards, and they all exhibit the same behavior. However, while two show no errors, one shows HICUROFS2 (not sure what that's about). They all work fine in another LDU I have.

I also ran some diagnostic tests:
- Diode test on DC terminals (and each phase): Read 0.643V, suggesting the IGBTs are in good shape.
- HV isolation test using a Megohmmeter: Measured 4.98MΩ on all phases and DC terminals, which is within Tesla’s specifications.

At this stage, I'm unsure what to try next. I’d appreciate any advice on further diagnostics or steps to identify the issue.

LDU V6 Board - FW: 5.35.R-sine, Web: v2.3

params.json

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[P.S.Mangelsdorf]

They all work fine in another LDU I have.

So all three control boards work in one LDU, but not another? Do they work in another LDU with the same input voltage/source you are using to test this one? Also, when you power up the trouble LDU, do you see a red light on any of the gate drivers?

One other item (maybe should have been first) I see the status is pot pressed, rather than drive. I think this is coming from the late firmware version, you might need to give it a brake signal before it will "go into gear". I might have that wrong though.

[nubster]

So all three control boards work in one LDU, but not another? Do they work in another LDU with the same input voltage/source you are using to test this one? Also, when you power up the trouble LDU, do you see a red light on any of the gate drivers?

One other item (maybe should have been first) I see the status is pot pressed, rather than drive. I think this is coming from the late firmware version, you might need to give it a brake signal before it will "go into gear". I might have that wrong though.

Hey, thanks. Yes. Well, the board that shows HICUROFS2 and another one work just fine in another LDU with the same battery (it's my test stand). I made a third new board just to be sure, but I haven't tried it in the "good" unit yet. I suppose I can try that to be extra sure.

When I power up the board, I see red LEDs flash on the gate driver boards, but just for a moment. They flash again when I power it off, but that's it. They don't turn on at all when applying throttle, etc. Here's a video I made for Great Lakes EV yesterday as they were helping me troubleshoot a bit.

Yes, it's the latest firmware (v5.35.R-sine). I didn't know about the brake signal thing. Do you mean the brake light switch or the actual brake pressure signal? I'll give it a shot. I'm not sure why it works on the other DU, though.

[johu]

It seems between the parameters and the spot values you have changed boost or udcnom? Because boostcalc is 29330 and expected is around 8000. But probably it is not the issue.
I see amp=29177 so it is generating a high amplitude sine modulation. No deraters in the way or anything. But that PWM seems to be lost on the way. You can try to follow it with a scope. PCB -> connector -> gate driver primary -> gate driver secondary -> phase output

[P.S.Mangelsdorf]

When I power up the board, I see red LEDs flash on the gate driver boards, but just for a moment. They flash again when I power it off, but that's it. They don't turn on at all when applying throttle, etc.

A failed stage will have a constant red LED on the gate driver, doesn't look like that is the issue.

Yes, it's the latest firmware (v5.35.R-sine). I didn't know about the brake signal thing. Do you mean the brake light switch or the actual brake pressure signal? I'll give it a shot. I'm not sure why it works on the other DU, though.

I believe its the brake light input, but Johannes can correct me - I'm still on v5.27, but if you're using the same testing set up on the other unit, that likely isn't the cause.

I would say do a check of the dumb things - are the AC bus bars connected to the motor (I messed that up once), is the encoder plugged in, is the internal wiring harness fully seated in the external connector, etc. Since it works on one drive unit and not another, I don't think it's a settings issue.

[nubster]

It seems between the parameters and the spot values you have changed boost or udcnom? Because boostcalc is 29330 and expected is around 8000. But probably it is not the issue.

Yeah, I tinkered with the boost a little, but it didn't help. I have since gone back to the base 1800 value.

I see amp=29177 so it is generating a high amplitude sine modulation. No deraters in the way or anything. But that PWM seems to be lost on the way. You can try to follow it with a scope. PCB -> connector -> gate driver primary -> gate driver secondary -> phase output

This is currently a bit over my head, but I'm willing to learn. Are those pins/schematics documented somewhere?
However, this is out of scope for the job I was asked to do. I was just supposed to install a new diff and perform a coolant delete.
I was concerned it was on the Openinverter side somehow, because the voltage being reported is wrong. Can you help me understand why it's reporting 77.34V when it's really only 60.84V?

I believe its the brake light input, but Johannes can correct me - I'm still on v5.27, but if you're using the same testing set up on the other unit, that likely isn't the cause.

The brake light thing didn't seem to work. I applied +12V to the brake light switch before and while I switched it to Forward, and then released it after. I would expect the board wouldn't go into Run mode if this were the case, but maybe I did it wrong.

I would say do a check of the dumb things - are the AC bus bars connected to the motor (I messed that up once), is the encoder plugged in, is the internal wiring harness fully seated in the external connector, etc. Since it works on one drive unit and not another, I don't think it's a settings issue.

Yes, I keep having the feeling like I am forgetting something really dumb like that. I keep checking, but apparently, it's so dumb, I can't see it yet!

Some additional context

This motor is a reman unit from a 2016 Model S. I got a call from a customer reporting that one of the axle tips broke off in the differential while driving, after which they immediately pulled over. They initially just wanted me to replace the differential and do a coolant delete mod. I didn't test spin the unit beforehand, as that seemed like a bad idea, considering it was full of metal debris. Upon opening the unit, I found a lot of debris at the bottom of the case, all over the oil pickup, and in one of the bearings. Fortunately, the gear teeth all looked fine. I replaced the differential and diff bearings and thoroughly cleaned the case and oil pickup assembly. I also performed the coolant delete mod. Before reassembling, I confirmed I could spin the gears and rotor by hand, so it wasn't locked up or anything. I'm using the Openinverter board to test that all is well again, but will reinstall the OEM board before returning it to the customer. I asked the customer to check the car for any error messages in case it could provide any hints to what could be wrong.

[P.S.Mangelsdorf]

Yes, I keep having the feeling like I am forgetting something really dumb like that. I keep checking, but apparently, it's so dumb, I can't see it yet!

Upon opening the unit,

Before reassembling, I confirmed I could spin the gears and rotor by hand, so it wasn't locked up or anything. I'm using the Openinverter board to test that all is well again,

Since you had the case open, triple check that you rebolted the motor connections.

Good to know the motor spins by hand.

I've worked on a unit that actually had the rotor shaft splines strip while driving, and that did not cause inverter issues, so I don't think the sudden loss of load killed something.

Just had a thought - you said you hear the whine start up. Does it stop at any point? (other than when you shut down) If so, when?

[nubster]

Since you had the case open, triple check that you rebolted the motor connections.

OMG. That was totally it! I've never been happier to be so dumb. Thank you!

I remember now that I started them by hand and got a phone call, which distracted me, and I never came back and torqued them down. They were only barely in with a thread or two.

Man. I really want to delete this post now, but I'm happy to leave it up no matter how embarrassing, in case it helps someone else. I need to put a poster up in my shop that says, "Remember to torque the phase bolts, dummy!"— lol

I owe you a beer or coffee; thanks, @P.S.Mangelsdorf!

[johu]

Literally nobody here has ever done such mistakes

grafik.png (79.61 KiB) Viewed 568 times

Great you solved it!

[P.S.Mangelsdorf]

OMG. That was totally it!
I owe you a beer or coffee; thanks, @P.S.Mangelsdorf!

Literally nobody here has ever done such mistakes

Glad I could help!

Don't feel dumb - I only know to point it out because I did the same thing two months ago.

[tom91]

I remember now that I started them by hand and got a phone call

Thats why any critical connection I paint pen mark them once done. That way I can always see before putting the covers/caps on if I done the step. Specially handy too to check is no-one opened something after it left your shop.

[nubster]

Thats why any critical connection I paint pen mark them once done. That way I can always see before putting the covers/caps on if I done the step. Specially handy too to check is no-one opened something after it left your shop.

Yes, normally, I do that once I button it up for good. In this case, I wasn't sure if I would have to open it again. They wanted me to service the rotor side, too, if needed. It's spinning great now, though, so I don't think it's necessary.

There was some coolant around the encoder wheel, and some rotor-bearing grease had oozed out a little, but I cleaned it up and did the coolant delete mod. Since the inverter side was clean and dry, it passed the HV iso test, and I could easily spin it by hand; I think they should be good to go.

[jrbe]

I remember now that I started them by hand and got a phone call, which distracted me, and I never came back and torqued them down.

One method is not snugging by hand until you can tighten them down. Having the nuts / bolts / something else hanging out as an obvious reminder helps a lot to avoid missing tightening things down.