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Hacking the Tesla Model S Front Junction Box

26K views 41 replies 12 participants last post by  Anatolii Efimtchik 
#1 · (Edited)
Further to the work undertaken on the Rear High Voltage Junction Box ("HVJB") by Jeff and Kenny, I've taken a look inside the Front HVJB :cool:

The Front HVJB has the following connectors;

"Brown" - HV to PTC Cabin Heater
"Orange" - HV to A/C Compressor
"Blue" - HV to DCDC
"Grey" - HV to Battery Fluid Heater
"Black" - LV signals

The HVJB also has a heavy duty earth strap and two holes for the HV input cables.
 

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#2 ·
Removing the cover is easy and reveals the HV connection (power feed from the Rear HVJB), lots orange insulating plastic, and a single PCB :)
 

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#3 · (Edited)
A quick look at the PCB reveals four HV fuses and a busy power circuit.

Fuse F1 (20A) connects the HV to the "Grey" connector via three IPB60R099CPA MOSFETs (here) and a .005R WSL2726 resistor (here). I suspect the busy power circuit is controlling the MOSFETs and has no connection with the other fused supplies.

Fuse F2 (40A) connects the HV to the "Orange" connector.

Fuse F3 (40A) connects the HV to the "Brown" connector.

Fuse F4 (20A) connects the HV to the "Blue" connector.

All HV connectors have HVIL pins that are connected to the PCB. The case lid and HV input cables also have detection switches.
 

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#4 ·
There is current measurement after the fets, see the curled up busbar.

Wait a minute, why would the fets control the HV to the 'grey' HV connector and measure current?

So would this mean that the PTC heater (water???) be a dumb module? Ah 2013 module looking at some info the battery heater just needs a pwm into the junction box.

Plus nice isolation devices (Big SMD packages) just like on the bms slaves.
 
#5 ·
So would this mean that the PTC heater (water???) be a dumb module? Ah 2013 module looking at some info the battery heater just needs a pwm into the junction box.
Yep... here's the key info :D
 

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#7 · (Edited)
To avoid going too much off topic in the Tesla Battery Heater topic (which of course is related), I have a question about the FHVJB.

What are the dimensions of the box?
(length/width/height) and size of the holes for the incoming power cable.
That allows me to create a dummy and explore possible locations in my car while looking for a FHVJB myself.

And is the corresponding plug for the control connector known?
Edit: sorry, see it mentioned above: Molex 33472-1201
 
#8 ·
What are the dimensions of the box?
(length/width/height) and size of the holes for the incoming power cable...
I've got it up on the bench at the moment.

Front HVJB
L : 9 1/4in case (10 3/4 to allow for LV connector and ground connection)
W: 8 1/4in case (9 1/4 to allow for HV plugs to AC,DCDC,etc. and HV in)
H: 2 3/4in case (3 1/4 if the mounting bracket still fitted)

HV hole size
less than 15mm, hard to get actual without disassembly, probably 13-14mm diameter.

Jeff
 
#11 ·
Finally I've found my FHVJB! I also have a Tesla service manual.
Now the question is, how to use the FHVJB to PWM control the heater?
Unfortunately 1 and ! isn't 2 for me at this stage.
Building on the connector X040 info Kevin shared earlier I'd been expecting 4 wires in the connector. In the box I see 6.
Connector numbering/layout
6/5/4/3/2/1
12/11/10/9/8/7
Then I see:
6 = White
5 = Yellow
4 = Red
12 = Blue
11 = Green
10 = Black
Electronics Electronic engineering Electronic component Technology Electrical wiring

Unfortunately besides the HVIL and Thermal controller I cannot find any reference in the wiring diagram that could help me in understanding what is what.
Has anyone already figured this out? Or a suggestion how I could approach this?
 
#12 ·
Front HVJB

inputs that I've tagged (but not verified with operation)

1 - blank
2 - blank
3 - blank
4 - OR 12v (orange)
5 - RD PWM in
6 - BL STAT out (PWM)
7 - blank
8 - blank
9 - blank
10 - BK Gnd
11 - YL-BL HVIL
12 - YL-RD HVIL

Note: also a large ground strap connected to the protrusion/nut just to the left of the low voltage connector

Connector : Molex 33472-1201 (I'm pretty sure)

Jeff
 
#13 ·
Thanks!
On scribd I found an newer version of the Tesla service manuals and those made more sense. I could trace your list back and came to the same conclusion. I think I'm staring to understand things ;) Should have gotten that manual much earlier.

I have measured and can conform the pins 11 and 12 as the HVIL lines.

And answers do trigger new questions:
- Can we do anything with pin 6 (STAT out (PWM))? Curious what kind of signal it will give.
- What are the characteristics of PWM in (pin 5)? Is that just a matter of assuming it's 12V (should be logic in a car) and try different frequencies?
 
#14 ·
And answers do trigger new questions:
- Can we do anything with pin 6 (STAT out (PWM))? Curious what kind of signal it will give.
- What are the characteristics of PWM in (pin 5)? Is that just a matter of assuming it's 12V (should be logic in a car) and try different frequencies?
My plan was to start with a 5v PWM signal, probably starting at 1Hz and working up (faster). Since the PWM is coming from a controller, I suspect they'll use 5v signals rather than a 12v. The Tesla pumps used a 1Hz signal - which caught me by surprise as I was expecting something in the 1kh range. I would guess that there is really only a need to send a PWM with a hertz that's twice as fast as the device can respond anyways. There's got to be some design balance between what is easy for the controller to parse (how easy it is to read the PWM signal) and how often it needs to see changes in the PWM.

I'm guessing the STAT will be something like 0-5v as a signal to the controller (outside the Front HVJB) that the heater is actually responding. Since the heater response is likely to significantly lag the controller instructions.

The control scheme would be something like 1) update the PWM, 2) wait for the STAT to get into the expected range. I feel some interesting tests coming on... pumping some coolant through the heater, sending PWM instructions, and then watching STAT and coolant temps to understand the response.

Jeff
 
#17 ·
I was wondering if this testing happened and where things landed on the PWM front. I am the point of connecting everything up in my build and wondered. If there is another thread that picked this up, let me know.

Also, I am using a FISKER coolant cabin heater (Eberspacher) over a PTC heater for my build, to allow the heated coolant to run through the RESTOMOD HVAC system (like an ICE vehicle) and planned to use the PTC HV connection for this heater, since the voltage for the Fisker (250-450VDC typ 350V DC) is similar to the voltage for a PTC heater. I chose this coolant heater because it runs on PWM heat demand signal 12V; active low (5k internal pull up resistor), 40-300Hz.

Any concerns or comments about powering this heater from the PTC slot on the high voltage distribution box?

Thanks!
Where did you source this heater? I've looked and no success.
 
#21 ·
Like what HV connectors are used on the Tesla HVJB? Those are KET HVSC 280 series, but they're not available to mere mortals :/

For reference:
  • Orange (A/C): MG655773 (key A)
  • Gray (fluid heater): MG655774 (key B)
  • Brown (PTC heater): MG655775 (key C)
  • Blue (DC-DC): MG655776 (key D)
 
#22 ·
Like what HV connectors are used on the Tesla HVJB? Those are KET HVSC 280 series, but they're not available to mere mortals :/

For reference:
  • Orange (A/C): MG655773 (key A)
  • Gray (fluid heater): MG655774 (key B)
  • Brown (PTC heater): MG655775 (key C)
  • Blue (DC-DC): MG655776 (key D)
Thanks.

Has anybody made an alternative to the infeed power connectors work? The jbox I bought doesn't have a cable.
Looking at the picture, the connector is just there to seal the round holes. The actual connections are on the inside of the jbox.
 
#35 ·
If I understand correctly by looking at the PCB and the previous posts in the thread... All devices (except the fluid heater) are merely connected via fuses to the HV input, i.e. no control via the FHVJB.

The heater is controlled via PWM inside the box. If you think of PWM at 0% as heater off and at 100% heater fully on, then, yes, it can be viewed as an equivalent to a contactor, where contacts open = heater off, contacts closed = heater fully on.

Hope this explains.
 
#38 ·
Добрый вечер, подскажите пожалуйста Я имею tesla model s 2015 года, сейчас начались проблемы с зарядкой, ввиду того что нагреватель основной основного аккумулятора не работает, то есть не подогревает батарею. Пришёл к выводу что либо неисправен предохранитель в передней коробке высоковольтной либо неисправен сам нагреватель основной аккумуляторной батареи точка у меня вопрос можно ли или должно ли присутствовать высокое напряжение на сером разъёме без движения? И ещё вопрос можно ли допустим серый разъём подключить на разъём который отвечает за обогрев салона, он у меня работает, это чисто для проверки основного нагревательного основного нагревателя для аккумулятора.
 
#39 ·
Most reincarnation of salvage Teslas is done in Ukraine - that's where most of the winning bids I've seen at salvage auctions go.

While we use Tesla pieces, I'm not sure many, if any, that are here actually work on restoring the car itself.

You should also post in English, even if it means using google translate.
 
#40 ·
Good evening, thank you for answering my question. The car was bought from America, to Belarus, in 2022, we encountered a problem only now. When the frosts became -20°, the car refused to charge, we found out that there was no heating of the main battery, so to find out the reason ,question, is it possible to connect the gray connector to the connector that is responsible for heating the interior? Or should I look at the fuse in the front high-voltage box?
 
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