PTC Heater & FJB extraction from dual motor car

[Cheburashka]

Symptoms: heat no worky. No customer facing errors. Dec 2016 75D

Service mode shows two active alerts:
THC_w0220_PTC_PtcFault
and
THC_d0015_cabinPTCHeater

HV system diagnostics also show a malfunction in the PTC Heater.

My first reaction was to check the fuse for the heater BUT it's contained in the FJB and since this is a dual motor the service manual says to remove HV battery and reach it from the bottom.

Obviously not practical. I havent taken things apart yet, but how hard is it to get at the FJB from on top?

Also, there is probably a strong possibility that the PTC Heater is booked and needs replacing along with a fuse replacement.

A few questions:
- Does new PTC Heater need redeploy by Tesla SC or can I swap parts?
- Any way to diagnose existing heater to check operation? Maybe measure impedance? I have no idea.

Any pointers appreciated.

Any pointers to an independent service (that isn't Tesla SC) in the SF south bay/San Jose area also appreciated.

 

[Cheburashka]

Does anyone know if I can test for power at the PTC heater to check on the fuse?

 

[Retkimora]

Does anyone know if I can test for power at the PTC heater to check on the fuse?

Yes, it is possible. Be careful, there might be high voltage under the plastic cover.

Plastic cover can be removed without tools or at least with minimal tools, maybe a knife or similar blade. There are 4 plastic clips holding the top cover on. Under the cover you'll see two orange wires going to posts. Measure dc voltage with suitable multimeter across these posts. See picture attached.

If hv loop is disconnected it should read almost zero after few minutes.

 

[NV Ray]

Yes, it is possible. Be careful, there might be high voltage under the plastic cover.

Plastic cover can be removed without tools or at least with minimal tools, maybe a knife or similar blade. There are 4 plastic clips holding the top cover on. Under the cover you'll see two orange wires going to posts. Measure dc voltage with suitable multimeter across these posts. See picture attached.

If hv loop is disconnected it should read almost zero after few minutes.

Great pic, thx. The yellow ethernet port - is connected to anything. What is it's purpose?

 

[Retkimora]

Great pic, thx. The yellow ethernet port - is connected to anything. What is it's purpose?

I think its the CAN port. If you unplug it the car will tell you there is no heater available. Mobile app won't let you enable blower or even seat heaters. I'd say leave it plugged in even if your heater element is not working.

 

[Retkimora]

My first reaction was to check the fuse for the heater BUT it's contained in the FJB and since this is a dual motor the service manual says to remove HV battery and reach it from the bottom.

Obviously not practical. I havent taken things apart yet, but how hard is it to get at the FJB from on top?

I'd say it is as hard from the bottom as from the top. I did it from the top today. Hardest part is getting the actual box off the firewall or even the cover off if you were to leave the box in place. Replacing the cover is as hard as getting it off. Everything else is pretty straightforward but time consuming. You need to remove wiper mechanism and move vacuum reservoir out of the way. Then you have barely the space you need to undo cover bolts.

 

[Cheburashka]

I'd say it is as hard from the bottom as from the top. I did it from the top today. Hardest part is getting the actual box off the firewall or even the cover off if you were to leave the box in place. Replacing the cover is as hard as getting it off. Everything else is pretty straightforward but time consuming. You need to remove wiper mechanism and move vacuum reservoir out of the way. Then you have barely the space you need to undo cover bolts.

Awesome to know.

How did you not lose any of the bolts when removing them? Magnetic bits? I'm thinking of getting some for the job. Do you remember if it's torx?

Did you have to unplug all the cables from the FJB?

Sorry these might be dumb questions but I haven't started on this yet. Figuring out where to get new PTC and fuse.

 

[Cheburashka]

Also did you end up leaving the box in place and just taking the cover off or removing the whole box?

Thanks!

 

[Retkimora]

Also did you end up leaving the box in place and just taking the cover off or removing the whole box?

Thanks!

Yes, it was easier to remove lid only. Lid is on with bolts, 8mm wrench or socket. All the other parts require 10mm and 13mm tools. Windshield wipers were 17mm. Plastic trim removing tool is useful too as wiring harnesses are held on with plastic clips. Same for the tray that is under windshield wipers.

And yes, I lost one lid bolt there and a 10mm socket as well. They fall all the way down to plastic cover thats under the motor. Haven't taken that one off yet.

 

[Retkimora]

Did you have to unplug all the cables from the FJB?

This seemed impossible for me so no, I didn't unplug cables. Main hv inputs could have been removed, they are on with big torx bit, likely T30 or even T40. It might help with lid bolts. Most of cables were so nicely stuffed against firewall covering that they wouldn't move at all. I still wonder how the ranger would have done it.

 

[Cheburashka]

This seemed impossible for me so no, I didn't unplug cables. Main hv inputs could have been removed, they are on with big torx bit, likely T30 or even T40. It might help with lid bolts. Most of cables were so nicely stuffed against firewall covering that they wouldn't move at all. I still wonder how the ranger would have done it.

Awesome. Thank you so much for this advice.

Was it easy to snake the old PTC heater cable out and put the new one in? Did you use a string for that?

 

[KalJoMoS]

Wouldn’t you want to use the current wire, you only need unscrew the faulty unit at the cabin end and use the cable ends on the new?

 

[Cheburashka]

Wouldn’t you want to use the current wire, you only need unscrew the faulty unit at the cabin end and use the cable ends on the new?

Yeah I think that's what I will do. Makes sense. The new PTC comes with a new HV cable though.

 

[Happy Kappy]

Just had the same errors pop up today. Checked fuse in frunk fuse box and it was good. Swapped PTC heater with a spare I had (1. no need for redeploy and 2. just disconnected the three wires under the cover of the PTC vs trying to replace cable) and it didn't work. Let me know if anyone else was able to fix and and what did it.
Thanks

 

[Cheburashka]

Just had the same errors pop up today. Checked fuse in frunk fuse box and it was good. Swapped PTC heater with a spare I had (1. no need for redeploy and 2. just disconnected the three wires under the cover of the PTC vs trying to replace cable) and it didn't work. Let me know if anyone else was able to fix and and what did it.
Thanks

Interesting. Did you measure voltage at the PTC heater with the car on?

 

[Retkimora]

Was it easy to snake the old PTC heater cable out and put the new one in? Did you use a string for that?

I used the old cable. It would have been possible to replace the cable using that string method though. Otherwise it requires long arms.

 

[Wazmat]

Symptoms: heat no worky. No customer facing errors. Dec 2016 75D

Service mode shows two active alerts:
THC_w0220_PTC_PtcFault
and
THC_d0015_cabinPTCHeater

View attachment 880374

HV system diagnostics also show a malfunction in the PTC Heater.

View attachment 880375

My first reaction was to check the fuse for the heater BUT it's contained in the FJB and since this is a dual motor the service manual says to remove HV battery and reach it from the bottom.

Obviously not practical. I havent taken things apart yet, but how hard is it to get at the FJB from on top?

Also, there is probably a strong possibility that the PTC Heater is booked and needs replacing along with a fuse replacement.

A few questions:
- Does new PTC Heater need redeploy by Tesla SC or can I swap parts?
- Any way to diagnose existing heater to check operation? Maybe measure impedance? I have no idea.

Any pointers appreciated.

Any pointers to an independent service (that isn't Tesla SC) in the SF south bay/San Jose area also appreciated.

Hey how are you reading these codes? Can you share please? thanks!

 

[howardc64]

Hey how are you reading these codes? Can you share please? thanks!

Its service mode, here is info on how to enable it

Howards Model S - Parts & Diags (google.com)

 

[Wazmat]

Thanks so much @howardc64

 

[Wazmat]

@howardc64 I have question for you regarding connecting with Tesla using toolbox3 and a laptop. Do you mind sharing your contract info?