Tesla SDU main contactor not closing  [SOLVED]

Topics concerning the Tesla front and rear drive unit drop-in board
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nubster
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Re: Tesla SDU main contactor not closing

Post by nubster »

qmedia2651 wrote: Wed Dec 22, 2021 11:23 pm Hopefully this one will be OK
Did you ever get this resolved/was it a bad inverter? The thread seems to indicate it was solved but I don't see a resolution and I'm having a similar issue...

Precharging seems to work ok but the main contractor never closes. The inverter status shows "WaitStart".

- Using an eBike battery for testing (~67v charged).
- Set udcmin to 0v and udcsw to 57v
- Applying +12v to pin 13 causes the precharge contactor to close
- udc spot value then shows: 67.81v
- status: WaitStart, lasterr: NONE, opmode; Off

My understanding is that at this point when I apply +12v momentarily to pin 9, the main contactor should close and the status should change to "RUN". Is this understanding correct?

However, when I apply +12v to pin 9 (IGN Start) nothing seems to happen. If I try to start the inverter in manual mode the precharge contactor opens but the main contactor never closes.

I also tested the voltage of pin1 of the 24-pin connector on the open inverter board after pre-charging (using the case as ground) and I got .4mv. Not clear on what this means or how to proceed. FWIW - This is a brand new/unused front SDU.
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Re: Tesla SDU main contactor not closing

Post by johu »

nubster wrote: Tue Jan 03, 2023 12:05 am My understanding is that at this point when I apply +12v momentarily to pin 9, the main contactor should close and the status should change to "RUN". Is this understanding correct?
absolutely. Does it change to "run"? Do you see din_start momentarily go "On"?
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Re: Tesla SDU main contactor not closing

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johu wrote: Tue Jan 03, 2023 11:08 am absolutely. Does it change to "run"? Do you see din_start momentarily go "On"?
Negative. din_start value does not change.

Just to be sure I plotted it but it stays 0 the whole time when applying +12v to pin9. I'm directly touching the pin9 Molex harness wire to +12v (no switch). Using EV200AAANA relays for both the main & precharge contactors.
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Re: Tesla SDU main contactor not closing

Post by johu »

ok, time to open up the inverter (in case you closed it). Check for cold solder joint. between Pin 9 and the processor there is only R52, a 1k resistor. Please check its continuity as well.

How about signals forward and reverse, do these change state when you apply 12v?
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Re: Tesla SDU main contactor not closing

Post by nubster »

johu wrote: Tue Jan 03, 2023 8:52 pm ok, time to open up the inverter (in case you closed it). Check for cold solder joint. between Pin 9 and the processor there is only R52, a 1k resistor. Please check its continuity as well.

How about signals forward and reverse, do these change state when you apply 12v?

OK, I'll open it back up and check.

Interestingly, I can get it to go into Reverse but not Forward. Meaning, dir says: "Reverse", but the main contactor still never closes.
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Re: Tesla SDU main contactor not closing  [SOLVED]

Post by nubster »

Yep, it appears to be a connection problem.

Opened it back up and connected everything and this time it went right into "Run" status as soon as I gave pin9 +12v. All the contactors did the right thing, and I can also put it into Forward/Reverse. Didn't change anything.

After further testing, I was able to determine that a little bit of torque needs to be applied laterally (perpendicular to the long side) to the side of the Molex connector, otherwise the signal doesn't make it. The harness I'm using is a used one from eBay so I'll make a new one from scratch and hopefully, that solves it.

Thank you so much for your help!
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Re: Tesla SDU main contactor not closing

Post by johu »

Great, thanks for your feedback :)
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Re: Tesla SDU main contactor not closing

Post by IGAVDUB »

johu wrote: Sat Dec 11, 2021 10:01 am SDU board gets a voltage signal on pin 1 of the 24-pin gate drive connector. Whats the voltage on pin 1 with HV on?
Hi, first sorry if this is in the wrong area but it relates to the UDC.
I have 1.71v on my UDC with the logic V7 board connected to the inverter and 120v DC supply, with the logic board separated from the inverter so no connection at all to pin 1 - 11 of the 24 pin (conn 5) I get 167.37V in the UDC field and upon testing the voltage on pin 1 -11 I have 0.9v.
I have added 1.5v to this and I get a UDC of 211.28V.

My question is should I be getting the 0.9v on the pin 1 with it separated from everything and it show 167.37V in the spot UDC field if I have no voltage ?

when I connect the logic board to the inverter it has the 1.71V UDC with or without the 120V connected.

everything else works in term of seeing the pot values change, direction, run, recharge cut out if UDCSW is set above 0v to say 3v at this point.
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Re: Tesla SDU main contactor not closing

Post by johu »

IGAVDUB wrote: Tue Feb 14, 2023 8:30 pm with the logic board separated from the inverter so no connection at all to pin 1 - 11 of the 24 pin (conn 5) I get 167.37V in the UDC field and upon testing the voltage on pin 1 -11 I have 0.9v.
Yes that is normal behaviour for floating ADC pins
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Re: Tesla SDU main contactor not closing

Post by IGAVDUB »

johu wrote: Tue Feb 14, 2023 8:43 pm Yes that is normal behaviour for floating ADC pins
Thank you,
From this I assume it's the volt sense on the Tesla inverter side.
I just didn't want to put it in another SDU without checking.
The 1.5v check did confirm this but I wanted to ask.
second hand part with no history is no fun!

Thank again.
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