Large Drive Unit Isolation Resistance

[Testurs]

Hey all,

I have not yet seen a dedicated thread regarding isolation resistance of drive units (in my particular case, the large drive unit). I have been assessing the coolant failed large drive unit from my 2012 Model S and it has about 5.7 mega ohm when the leads are connected to the case and the top post (while the three stator posts are bolted). I saw another thread where anywhere from 4 to 120 mega ohm was listed as normal - surely the true range must be narrower. I do believe that my coolant failed LDU failed because the logic board got damaged, not because of the stator windings (I was able to confirm the logic board failed because I got unusual characters when I attempted to read the board on toolbox).

If others have readings for isolation resistance or specs (tesla's link does not work), please post it here, many will benefit when they attempt to diagnosed their drive units.

 

[tastyguac]

In developer mode, I saw as low as 80 kohm in the vitals screen with the contactors open. If I remember correctly, my isolation tester/megaohm meter read 0 when I probed the case to either DU HV inlet posts.

The coolant leak can cause anything from corroded windings of the stator (causing a short) to electrical issues within the inverter. Usually the service alerts will point you to the actual issue if its iso resistance failure or an electrical failure in the inverter.

 

[evrepair]

Anything higher than approximately 5 megaohm should be good. (On the model S its normal for whole car isolation to be approximately 1,500 kohm BTW)