Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Used DC/DC converter?

This site may earn commission on affiliate links.
I bought a 2014 Model S that have done 270000km (Yes, I live in Sweden so we talk km ;))

Long story short: I believe my DC/DC converter is broken (does not charge the 12v battery, I have 386v from the front junction block). Instead of towing it to Tesla (300km away) and paying them big money to fix it, I'm thinking about replacing the converter with a used one.
The question is: can I do it or does the "new" converter need to be coded/paired to my car?

I hope you understand my question and that someone can help me. I'm very thankful in advance!

/ Tomas
 
If the converter has firmware that needs to match the car's firmware, you'll need a firmware redeploy after you do the swap.

I did this with the onboard charger and it threw 13 different error codes for just mismatched firmware. Nightmare...if you can't push firmware yourself.

Firmware....needed to say it one more time...5 is my unlucky number...
 
there should be 3 fuses

I could only find 1 fuse in the DC/DC converter, but 4 (AirCon, PTC, BatHeat, DC/DC) in the junction block/distribution module.
I don´t have the converter located in the wheel arch. I found a picture (not mine) of how it looks in my car. The left arrow points at the junction block with 4 fuses. The right arrow points at the DC/DC converter.

DCDC.jpg

I realize I never told you my problem, so here it comes:

I have bought a 2014 Model S that "broke down" with messages pointing at the 12v-system (see attached picture).

20220913_212413.jpg

I have done some measuring/troubleshooting myself and have come to following conclusions:

12v or below on the lv-battery.
387v in the front distribution module
Fuses in the front distribution module are ok
387v in the dc/dc converter
Fuse in the dc/dc converter are ok
12v or below out of the converter
Air condition compressor 500ohm
PTC 500ohm
Battery Coolant heater 50ohm

From time to time the car comes to life and I can put it in gear and drive it.

My guess is the dc/dc converter, but I don't know if the "system" shuts it down in case something else is wrong.
If there is an isolation problem, in my mind it would shut the HV down?

Any ideas of what to measure or look at?

(Today the car is ok and I drove it to work, but I don´t know if it will take me home :))
 
If the converter has firmware that needs to match the car's firmware, you'll need a firmware redeploy after you do the swap.

I did this with the onboard charger and it threw 13 different error codes for just mismatched firmware. Nightmare...if you can't push firmware yourself.

Firmware....needed to say it one more time...5 is my unlucky number...
Thank you for the tip (found your thread)!
I found out that I can enter Service Mode at home, so it should work.
 
Thank you for the tip (found your thread)!
I found out that I can enter Service Mode at home, so it should work.
When the car doesn't want to turn in Drive did you try to jump the 12V battery with an external power source? If you can put it in drive with an external power source I think it is safe to say it has nothing to do with HV. Also I don't see any HV isolation faults.
 
When the car doesn't want to turn in Drive did you try to jump the 12V battery with an external power source? If you can put it in drive with an external power source I think it is safe to say it has nothing to do with HV. Also I don't see any HV isolation faults.
That´s a bit unclear... I did manage to get it into Drive one time with another 12v-battery and charger.
At the moment I´m leaning towards bad ground-connection. I don´t remember where I put the starter cables when I was able to put it into Drive, but I do remember that I had them both directly on the battery and on the positive and ground at the front of the car. Maybe that was why it only worked once? I will try to clean up some ground-connection and hope for the best :)
By the way, it´s working fine right now, for the second day.
 
I could only find 1 fuse in the DC/DC converter, but 4 (AirCon, PTC, BatHeat, DC/DC) in the junction block/distribution module.
I don´t have the converter located in the wheel arch. I found a picture (not mine) of how it looks in my car. The left arrow points at the junction block with 4 fuses. The right arrow points at the DC/DC converter.

View attachment 852349

I realize I never told you my problem, so here it comes:

I have bought a 2014 Model S that "broke down" with messages pointing at the 12v-system (see attached picture).

View attachment 852350

I have done some measuring/troubleshooting myself and have come to following conclusions:

12v or below on the lv-battery.
387v in the front distribution module
Fuses in the front distribution module are ok
387v in the dc/dc converter
Fuse in the dc/dc converter are ok
12v or below out of the converter
Air condition compressor 500ohm
PTC 500ohm
Battery Coolant heater 50ohm

From time to time the car comes to life and I can put it in gear and drive it.

My guess is the dc/dc converter, but I don't know if the "system" shuts it down in case something else is wrong.
If there is an isolation problem, in my mind it would shut the HV down?

Any ideas of what to measure or look at?

(Today the car is ok and I drove it to work, but I don´t know if it will take me home :))
Are you measuring the resistance from each harness of the HV components? I have a similar issue where my DCDC converter is not providing power to the 12v (no HV power from battery I do not hear the contactors go on likey due to the DCDC converter).