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Salvage Model S P85D Contactors Not Closing

GazMav

Member
May 19, 2021
9
7
UK
Hi All,

I have done lots of research and purchased a damaged P85D, this had a low front-side impact (left side), taking the wheel clean off:
  • No airbags have gone off
  • The emergency loop was cut
  • Pyro fuse near battery didn't blow
  • Car was dead on arrival and needs the 12v battery jumping
  • Car powers up on jump, battery not charging from DC-DC charger
  • I haven't checked the 225a fuse yet.
  • The car reports 9 mile range but understand this was the last time the battery was engaged
  • I'm sure there is low/no AC gas
  • The two HV cables that connect to the front motor did get damaged from the wheel impact , I could see a tiny bit of copper (temp repair, will replace) so suspect the HV went to body ground and blew a fuse, this has a fuse inline with the cable (under back seat) but I can't see that effecting the contactors?
  • Car has been sat for nearly 2 months
I was hoping I could reconnect the cut loop and drive off into the sunset, unfortunately I don't hear the contactors close, the car comes up with the usual low power errors, I did repair the coolant pipes and replace the coolant so that error has gone.

I can open the charge flap but the port is locked and will not unlock from the screen.

I plan to check the 225a fuse soon but does anyone have any ideas what fuse could have blown that is causing this? - Can the inline fuse be checked?
I am fully aware of the risk and will take safety precautions when dealing with the HV system.

Thanks all,

Gaz
 

rooter

Member
May 13, 2018
773
949
Edmonds, WA
It's not a good idea to tamper with the inline fuse until you replace that cable. Its shielding could be shorted to the hot lead. Test the fuse as any other -- out of the circuit.

It would be useful to put it into diag or factory mode in order to get comprehensive error reporting, which means rooting the CID.

And never forget -- 400vDC will kill you dead.
 
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GazMav

Member
May 19, 2021
9
7
UK
It's not a good idea to tamper with the inline fuse until you replace that cable.
Thanks Rooter,
I've ordered the HV cable + fuse , Tesla UK would sell me one but for £436.
I'll replace that and try again, then try to grab some logs if it still doesn't work.
 

GazMav

Member
May 19, 2021
9
7
UK
Hi All,
Finally replaced the HVJB to front drive motor fuse and cable, and with a good charge on the 12v battery I get...

  • Codes BMS_f086, BMS_w086, BMS_w023, BMS_w026
  • Can't hear the contactors closing still and 12v battery not getting charged.
  • The car reports 10 miles of range now whereas before it reported 9?!
I've seen software that reset code w026 but stuck with the rest, Can anyone help me work out what the rest of the codes mean please?
Does anyone in North West England have T_Diag I can hire please?


The only damage to the HV system was that blown fuse and damaged cable so now I've replaced it I'm confused why I'm having so much trouble.

Thanks All,

Gaz
 

rooter

Member
May 13, 2018
773
949
Edmonds, WA
You don't say what year but it'll be 2014 or 2015.

f=fatal, w=warning

BMS_f086_Not_Ok_To_Precharge

Precharging, front-loads the circuits with voltage so there isn't a surge when demand is made. (Same principle in hydraulics)

Looks to me that your contactors have a problem, maybe welded. (Everyone else will be too cowardly to make an diagnosis like this) I will also say that your car does not have Ludicrous mode, and thus does not have the more robust inconel contactors which later models have, that avoids this problem.
 

GazMav

Member
May 19, 2021
9
7
UK
Thanks @rooter
BMS_w023_SW_Contactors_Open_HWOC
BMS_w026_SW_Ctrs_Disabled
BMS_w086_SW_Not_OK_To_Precharge
BMS_f086_SW_Not_Ok_To_Precharge

I've read about w023 and w026 when the BMS detects a hardware overcurrent (when the front HV cable grounded to the car and blew the fuse) and wondering if you have to clear these before the car will even try to precharge.
This also makes sense that I get the w086 codes as the BMS says the car is not OK to precharge like it's not even trying due to the stored code (I've read about other codes for precharge too long etc), in my opinion it's not even trying to precharge and open the contactors so I can't jump straight to damaged contactors.

Is there anything else to try before I jump in and drop the battery? I think I should try to clear the 023/026 codes first.

Any input is really appreciated,

Thanks,

Gaz
 

rooter

Member
May 13, 2018
773
949
Edmonds, WA
Clearing the codes can be done with Toolbox as you likely know, but I have no experience with that. I am confident that it can be done if you're rooted, but I've never had this problem; anything I know is from my own experience. I suspicion that the codes are held in the gateway.
 
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GazMav

Member
May 19, 2021
9
7
UK
Quick update. w026 did clear but 086 and 023 did not.

I assume this means bad news? :)
BMS_contactorState Weld
thumbnail_20210608_203444.jpg
 

GazMav

Member
May 19, 2021
9
7
UK
Another update, maybe it will help someone in future :)

I removed the battery and @rooter was correct that the negative contactor was welded closed. I replaced the contactors:

1625644759340.png


I then refitted the battery but made the mistake of not making sure the main data connectors were fully in, this caused lots of warnings and errors (BMW_MIA) etc, I then managed to reach over the top of the battery and fully clip the connector in.

Some of the codes cleared on their own but I'm still left with BMS_w023_SW_Contactors_Open_HWOC (Hardware Over Current).
I also have a new code after refitting battery: BMS_f036_SW_HVIL (HV Interlock) which I'm really hoping was just due to the unplugged connector and isn't a switch not engaged on the lid of the BMS.
The car is still not attempting to close the contactors, my precharge warnings have gone so I am slightly further along.

1625645163913.png


I'm going to hire T-Diag again and try to clear these, one thing I noticed is that T-Can has a button to clear w023 but T-Diag doesn't.

Any advice or suggestions at this point would be a massive help, I'm running out of ideas now :(
 

rooter

Member
May 13, 2018
773
949
Edmonds, WA
Well done.

I hope:
- You'd disconnected the 12v battery and pulled the emerg responder's loop before doing any/all of this work;
- You've replaced both contactors with inconel ones. If so this problem will never happen again.

It's not lying about the HVIL fault. This could be any switch in the interlock loop, and will clear once fixed.

And I'm puzzled how you were able to 'reach over the battery and connect the low-voltage connector'. That is integral to the pack and can't help but connect, unless its mating connector somehow got loose.

Dropping the pack is lots o' fun, isn't it?

To all: What GazMav has done is an extremely risky operation and you should not attempt it unless you're highly technically adept. 400vDC will kill you dead.
 

GazMav

Member
May 19, 2021
9
7
UK
Well done.

I hope:
- You'd disconnected the 12v battery and pulled the emerg responder's loop before doing any/all of this work;
- You've replaced both contactors with inconel ones. If so this problem will never happen again.

It's not lying about the HVIL fault. This could be any switch in the interlock loop, and will clear once fixed.

And I'm puzzled how you were able to 'reach over the battery and connect the low-voltage connector'. That is integral to the pack and can't help but connect, unless its mating connector somehow got loose.

Dropping the pack is lots o' fun, isn't it?

To all: What GazMav has done is an extremely risky operation and you should not attempt it unless you're highly technically adept. 400vDC will kill you dead.
Thanks @rooter
I was very careful and yes, it was 'fun' dropping that battery on my driveway without a lift :)

So as I raised the pack back into the car (I had alignment rods in) the mating connecting on the low voltage side didn't clip all the way in, it just needed a tiny push from the top, I reached over the rear bar (sorry don't know the name) and felt it clip in with a small push from the top.

The more I think about it, I wonder if the HVIL error is from the HV connector not fully seating?, If you look at the service manual they have a special tool that pushes the connector fully in.
Looking at the HVIL system, there is a small rod on that connector that has to engage fully. I am going to try this later and see if the fault clears, I'm hoping as this is the only fault and the others are warnings it might all come to life :)
 
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GazMav

Member
May 19, 2021
9
7
UK
What a beautiful noise those contactors make when they close!

The HV connector was not connected, it had pushed back into it's holder, I dropped the pack again, removed the connector and setup correctly then as the pack was lifted to the car I had a small camera making sure it went it, still needed a final push home.

No more f036 HVIL fault, still a w023 warning but I can reset that at a later date.

Car now drives and charges.

Thanks again @rooter , your "It's not lying about the HVIL fault." really made me think it must be that pack connection as it was the only thing I touched.
 

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