Using Tesla thermal management system parts

In the first post about the battery thermal management I discussed the importance of keeping batteries in their ideal temperature range. Now let’s look at how Tesla approaches this. I will explain the various components of the Tesla thermal management system and where possible offer relevant connectors and information so you can use Tesla components in your electric car conversion project.

As discussed in the temperature blogpost cooling or heating an electric car battery is possible using air or liquid. Tesla has adopted the liquid cooling approach.

System layout overview

Below is a simplified sketch of the cooling system in a Tesla Model S. I omitted The DC/DC converter and the chargers and some other details.

Note on the 3-way and 4-way valves. It turns out there are two models of each type. They have the same part number but the orientation / logic of the outlets is different.

Initially this blog post contained the things I found as per logic 2. Then I wanted to connect another valve and went to my own website and that info turned out to be wrong for that one. So I assumed I initially made a mistake perhaps by swapping front and back view. So I changed the blog to the representation as per logic 1. And then later I got another valve that behaved like the initial one I had….. As a result, now I publish both. Please do check which one you have.

1. Tesla battery modules cooling/heating

Each battery module in a Tesla Model S and Model X battery pack has a thin aluminum tube in between the 18650 cells. The P100 modules even have two tubes for enabling cross flow. Therefore, the heat exchange in those modules is even better. A 13 mm internal diameter tube running along each side of the battery pack has 8 mm branches with corrugated tube connecting all battery modules in parallel. In other words, all modules are receiving coolant of similar temperature. Connecting them in series would result in an uneven temperature distributing since the first modules are in favor. In addition, it results in a big pressure drop.

battery module flow test
I did a flow and pressure test comparing Tesla battery module cooling in series and parallel.

Tesla uses quick connect fittings with manual lock on the battery modules. NB. The 6,3 kW modules from a Tesla Model S P100D use different coolant connectors. These are now also available.

On each 5,3 kWh battery module there are two coolant connections. This is a standard SAE 5/16″ quick connect. Officially the J2044 buit often found as fuel line quick connects. Tesla uses connectors with manual lock (below an image of an aftermarket connector with manual lock).

Tesla battery module cooling connector straight

The seal at the hose end is especially needed when a nylon hose is used. Tesla uses ID 6 mm tube, but connectors with ID 8 mm are also available.

2. Tesla battery heater

Once source of heat for the battery is an electric battery heater running from the high voltage battery pack. This is a sheath heater with a capacity of approximately 5 kW. You can find two different types in the Tesla Model S. Early models (2013 and 2014) had one from Philips & Temro Zerostart. I believe these are prone to failure and can result in isolation errors. Therefore, from modelyear 2015 onwards Tesla switched to a heater made by LG. You can recognize these by the black plastic back cover. The Tesla part numbers I managed to track down over the various model years are:

  • 1009508-00-E (2013) Philips & Temro Zerostart
  • 1028689-00-B (2014) Philips & Temro Zerostart
  • 1038901-00-E (2015) LG
  • 1038901-00-F (2015) LG
  • 1038901-00-G (2015, 2016, 2017) LG
  • 1038901-00-H (2017) LG
  • 1038901-00-I (2018) No longer has the LG logo but appears to be the same unit. Made by Tesla?
  • 1038901-00-J (2018, 2019) Also Tesla sticker, no LG logo

The model year indicates in what year a letter was first used. All heaters have the same form factor. The front high voltage junction box (FHVJB) (Tesla part number 1028843-00-B or 1028843-00-C) controls the battery heater and can reduce heating power/capacity via high voltage PWM.

The battery heater has a build in thermistor. It is an NTC thermistor. I measured the resistance at various temperatures and calculated the thermistor values. It is a 10K thermistor with a β of 5500 K.

Tesla battery heater thermistor measurement

Tesla water heater orientation

Tesla water heater correct orientation

The Tesla water heater should be used in the orientation where cold water flows in at the low end bottom and hot water flows out at the top. It should not be used sideways. Furthermore it is recommended that in the hose flowing towards the heater no air pockets can remain.

Tesla water heater wrong orientation

In addition, heat can come from the motor/inverter. In that case, waste heat from the drivetrain is used to heat the batteries. The system goes from two separate parallel loops into a series layout using the 4-way valve.

3. The 4-way valve

The 4-way valve (Tesla part number 6007370-00-B) can join or separate the batteries coolant loop from the rest. In other words, if the battery temperature is below the ideal operating range the 4-way valve will join the two circuits. Similarly, as soon as the batteries have reached their ideal operating temperature range the valve will separate the two. In that configuration the radiator is available to cool the drivetrain. Therefore, if the battery needs to be cooled, the active cooling using the airconditioning kicks in and the chiller is used.

The valve has three positions of which Tesla uses two. Be aware that there are two types found in Tesla’s under the same part number.

Orientation / logic 1

4 way in series input Gnd
Series mode
  • Input = GND
  • Feedback ≈ 10,5 V
4 way in parallel input 12V
Parallel mode
  • Input = 12V+
  • Feedback ≈ 2,5 V
4 way mixing signal nc
Mixing (not used by Tesla)
  • Input = Not connected
  • Feedback ≈ 6,5 V

Orientation / logic 2

The port numbering is the same since compared to the above it is front view vs rear view but the flow is different. But why??

4 way in series
Series mode
4 way in parallel
Parallel mode
4 way
Mixing (not used by Tesla)

First I’ll explain the 3-way valve and then I’ll get back to the input and feedback below in “Wiring the 3-way and 4-way valve” since this is the same for both valves.

4. The 3-way valve

Be aware that there are two types found in Tesla’s under the same part number

Tesla used two 3-way valves. In the Model S the part number is 6007384-00-B and in the Model X the part number is 1064225-00-C. These 3-way valves are used as bypass for respectively the radiator and the chiller.

In addition, in mixing mode, you can use it to divert the output of a (battery) fluid heater to both the battery and a fluid interior heater.

Also the three way valve has three positions. It has the same actuator and form factor with one outlet less, even the outlet numbering is consistent. The valve flap / ball is different though.

Orientation / logic 1

3 way input 12v include
Bypass mode
  • Input = 12V+
  • Feedback ≈ 2,5 V
3 way input Gnd include
Include mode
  • Input = Gnd
  • Feedback ≈ 10,5 V
3 way input NC
Mixing (not used by Tesla)
  • Input = Not connected
  • Feedback ≈ 6,5 V

Orientation / logic 2

The port numbering is the same since compared to the above it is front view vs rear view but the flow is different. But again, why??

3 way signal GND bypass
Bypass mode
3 way signal 12V include
Include mode
3 way signal NC
Mixing (not used by Tesla)

‘Bypass’ and ‘include’ are arbitrary. I’m not sure how Tesla exactly uses them and you can choose whatever is convenient in your build. Next question is: “How do we use and control these valves?” This is explained below in ‘wiring the 3-way and 4-way valve.

Wiring the 3-way and 4-way valve

Using the 3-way and 4-way valve in your project requires a small control system. The valve has four contact pins.

You need to provide the input pin with a signal (GND, 12V or NC) en then the feedback will show the indicated voltage as soon as the position is reached.

A =12V+
D =Input
F =Feedback

Currently I am working on developing a Tesla valve and pump controller. It will have some simple inputs either via CAN-BUS or analog to control these valve positions. It will also have a feature to control the below Tesla pump.

5. Water pump

Depending on the model year, Tesla used two or three electric water pumps in their cooling circuit. At least early models had a backup pump in the battery cooling loop. Once the 4-way valve separates the batteries loop from the rest, each loop has it’s own dedicated pump. I have seen various water pumps in the Tesla Model S and I am not sure which pump type / part number is used where exactly. The below information is for the 6007367-00-E and probably also applies to at least 6007367-00-*, 6008047-00-* and 6007373-00-*. Not tested yet myself so curious to hear your findings if you did. Full Tesla water pump parts number overview in “Connector kit water pump Tesla Model S / Model X“.

The pump has four inputs: 12V+, GND a PWM input for speed control and a PWM output for diagnostics. Both the pump and the mating connector are available at EVcreate.

Specs of the Tesla water pump

The nominal voltage is 13V (accepts 8V – 16V) and the maximum amp draw is around 7 A. In my view quite significant, so reducing pumping power via PWM if less flow is needed can be very beneficial. The fluid connections are 19 mm barb hose. Pump speed is 750 to 4700 RPM.

Mounting the Tesla water pump

The pump must be installed in such way that air cannot get trapped inside. In addition it is important that the pump is positioned low enough since it is gravity fed and not self sucking. This applies to most electrical (auxiliary) water pumps.

Allowed orientation

Allowed pump orientation

Not allowed orientation

No allowed pump orientation

Furthermore it is important to install the hoses in a way they to not create an axial load on the pump.

Wiring the Tesla water pump

The pump has four connections. Our Connector kit water pump Tesla Model S / Model X contains the mating connector, seals and terminals.

Tesla pump pin numbering
3=PWM input
4=PWM output
Tesla pump pinout

Controlling the Tesla water pump

Via pin 3 (see above) you can control the speed of the pump. It requires a switched to ground PWM signal. Not all inputs are valid. See below table and graph for the correlation. The normal operating range is defined by the following formula RPM = 68,8 x PWM – 550.

(pwm %)(RPM)
0 – 8Invalid input
8 – 120
13 – 17Invalid input
18 – 20750
21 – 79(65,8 x PWM – 550)
80 – 824700
83 – 100Invalid input
Pump PWM to RPM

If you do not provide a normal input after a short startup and diagnostics time (4 to 7 seconds) the pump will start running at full speed.

7. Airconditioning compressor

Tesla used a couple of different AC compressors. Early models (modelyear 2013 / 2014) used an ES34C by Denso and has part number 6007380-00-D. This one is PWM controlled.

Connect 12V + in to pin 7 and provide chassis ground to pin 1. Pin 4 and 8 are not connected (don’t even have a male terminal in the compressor connector). You can leave the power feedback (pin 5) and diagnostics (pin 3) unconnected too.

The compressor is enabled by grouding pin 2 (active low) and speed control via a PWM signal on pin 6.

1 =GND
2 =On/Off
3 =Diagnostics
4 =Not connected
5 =Power feedback
6 =PWM in
7 =12V in
8 =Not connected
Early Tesla airconditioning compressor
Connector Tesla AC compressor
Compressor view

Later models (CAN control unknown)

Later models (2015/2016) had a HVCC ESC33 and Tesla part number 1028398-00-E, 1028398-00-F and 1028398-00-J. Tesla also used the Hanon HES33 and is found with number 1063369-00-D, 1063369-00-E, 1063369-00-F and 1063369-00-G. Both later types are unfortunately CAN controlled and details unfortunately are unknown (so far).

I have adopted another approach and use a more lightweight Benling AC compressor. More details can be found in a separate blogpost.

8. Tesla chiller (battery heat exchanger)

Over the years Tesla used three different types of chillers. To be exact, they used three different block valves on the heat exchanger by Modine. The exchanger itself is also found with different part numbers:

TypeBlock valve part numberHeat exchanger part number
Block valve part number is leadingExamples, not an extensive list
TXV without solenoid1019541-00-BModine = 1E006836
Tesla = 1019540-00-C
TXV with solenoid6007362-00-CModine = 1E006773
Tesla = 1007476-00-D
EXV1039040-00-CTesla = 1037764-00-C
Tesla = 1037357-00-D
Modine = 1E007303

The EXV is the latest generation of expansion valves. It uses a control loop with a sensor that provides the right amount of refrigerant for the chiller. However, that requires a separate sensor and ECU. Above all, the control specs are unknown.

The TXV stands for Thermostatic Expansion Valve. Using the temperature it allows more or less refrigerant through. The TXV with solenoid is the most easiest DIY approach. You can just use the solenoid to allow the chiller to cool or not.

However, there are many Tesla’s, in particular early ones using the TXV without solenoid. My theory is that this works fine as long as you bypass the chiller in case no active cooling is needed (any input on this is welcome). Then there will be no cooling effect in the block valve and as a result it closes or even freezes. It is important though to not run the AC compressor when both the chiller and cabin are not requiring cooling. I will elaborate on this in a separate airconditioning topic.

Tesla chiller 6007362 00 C
Tesla 6007362-00-C

Barb hose internal diameter that fits the coolant inlet/outlet is 19mm.

The valve is normally closed. While powering the solenoid with 12V (polarity does not matter) it opens. I did a test and at 13,6 it draws 600 mA. You could consider using an economiser, for example the Texas Instruments DRV103.

9. Tesla cabin (evaporator) expansion valve

The cabin evaporator has a block valve / expansion valve with an integrated solenoid. In case battery cooling is required but cabin cooling is not.

In later models Tesla started using the EXV also for the cabin evaporator.

Blog series on battery thermal management

  1. Ideal battery temperature?
  2. Using Tesla thermal management parts
  3. Other OEM thermal management
  4. Example of DIY approach
  5. Battery temperature data in practice

Feedback welcome

Any feedback, additions, suggestions for improvement is welcome. Please contact me by e-mail.

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34 thoughts on “Using Tesla thermal management system parts”

  1. Dear Manager:
    I need to buy a complete schematic of the thermal management system Tesla Y to understand how it works. Can you tell me where I can get it? Thank you very much.
    Diego Gaynor

  2. Thanks for this info!
    Do you know if the 3 and 4 way valves also act as check valves or the have no restrictions?
    Thanks in advance.

  3. Can you please explain what controls the cooling effect?
    For example. Let’s assume ambient temperature in the car is at 25C and I want to lower it to 19C. At the same time the battery is at 27C and I want to lower it to 25C.
    Is it the temperature sensor in the evaporator (or in the cabin of the car) and a sensor in the battery cooling line which will control the PWM of the a/c compressor? Or there’re other methods?
    Thanks in advance.

    • That will certainly be a challenge. First you need to make sure the car closes it’s contactors by either going in charge or drive mode. Then you need to ensure the valves are in the correct position, run the pump(s) and take over PWM control via the front high voltage junction box. Plus all the stuff I’m forgetting right now.
      What is the use case? In what situation do you want to heat the battery when the Tesla currently does not?

      • Hi i came to a cheap tesla coolant heater.
        Do you have a protocol how to control this heater? is it PWM controlled or maybe CAN?
        I would like to use it in my EV conversion as supplemental heater inline to my webasto diesel heater. Since webasto does need like 10minutes or more to come on i would like to quickly get coolant to 55deg and then turn electric heater off when webasto takes over to higher temperature. That way i will have heating/defrosting even if my 6l diesel supply runs out…
        I will use webasto coolant pump and electric heater will only start with webasto.

  4. Is it possible to use a unified AC system to cool both batteries and cabin in a new build? Would it be possible to use refrigerant alone and no coolant?
    Idea being battery cooling can run independent of cabin, or cabin and batteries both get cooled concurrently when needed.

    • Yes, using an AC compressor to both actively cool batteries and cool the cabin is possible in a DIY setting. That is exactly what I did in my build. Compressor speed (ie cooling capacity) was a function of cooling requirement of cabin and/or batteries. And you need valves to exclude batteries or cabin if they do not require active cooling at te same time.
      Using refrigerant alone seems not feasible to me. I think the risk of locally freezing the batteries is quite high. Furthermore I’ve not seen this approach at any OEM. Especially since you often also want to be able to heat the batteries. Fluid has a nice heat capacity and helps in a gradual and even temperature control.

  5. Hello, Thank you for the detailed breakdown! How did you go about controlling everything / monitoring the temps?

    Did you run an Arduino(or similar) to control the valves, compressor, evaporators, etc?

    I would assume the evaporator valves are binary on/off – how would you deal with a situation where the batteries only need a little bit of cooling but the cabin AC is commanding the compressor to run at full blast?

    Thank you for your help!

    • Yes, I made an EV Peripherals controller. It controlled everything, pumps, fans, valves, displays, heater, airconditioning, remote control, etcetera. I am currently breaking that down in multiple controllers that can be used stand alone and are communicating where needed.
      The cabin and batteries shared the AC compressor. Depending on the required cooling capacity of each system the AC compressor would run at a certain speed (power). If the batteries only need a bit of cooling, then the target temperature would be reached quickly and then that system would be disconnected. Indeed the valves I use(d) are on/off. On top of that the blockvalves also regulate the amount of R134 going into the chiller and/or cabin evaporator. OEMs nowadays use eXV’s to control the amount of R134 for each system.

  6. Hi Lars 🫡
    My battery heater doesn’t pre heat my battery. Do you know if there is a fuse in the heater or should i just order a new heater?

    Thanks for this blog it’s been very helpful understanding my car.

    • In a Tesla? If the car is enabling the heater then indeed either the fuse is blown or indeed the heater is broken.
      In the teardowns I did the fuses were in the front high voltage junction box. So the box where the high voltage heater connector plugs into.

  7. For anyone wishing to use the Tesla coolant pump which is identical to the Nissan Leaf Coolant pump the sketch running on an Arduino Uno works to contro the pump speed.
    I’m not sure what the RPM is but if my maths are correct it’s around 2400rpm. I can see coolant flowing well but the pump is whisper quiet, even better the current draw fell from over 3A to under 500mA and the coolant is no longer cavitating which it was before.

    // Set-up fast PWM on the Arduino UNO at 1Hz on Digital pin D9
    void setup() {
    pinMode(9, OUTPUT); // Set digital pin 9 (D9) to an output
    TCCR1A = _BV(COM1A1) | _BV(WGM11); // Enable the PWM output OC1A on digital pins 9
    TCCR1B = _BV(WGM13) | _BV(WGM12) | _BV(CS12); // Set fast PWM and prescaler of 256 on timer 1
    ICR1 = 31249; // Set the PWM frequency to 2Hz: 16MHz/(256 * 2Hz) – 1 = 31249
    OCR1A = 14000; // Set the duty-cycle to approx 45%: 31249 / 45 = 14062
    void loop() {}
    (603 Bytes) Downloaded 1 time
    To change the pump speed by a small but noticeable amount increment/decrement OCR1A by 1000 at a time.

    Gnd on the Arduino is connected to 12V ground
    Pin 9 on the Arduino is connected directly to pin3 on the pump.

    Where I found the original sketch that I adapted … 2?u=alibro

  8. This is pretty damn great!

    BUT, in your top diagram, where’s the second input / output on the battery module – you only show one line going into the module?


    • The coolant is going in at number (6), the temperature sensor and is going out at the left hand side.
      I have updated the schematic by highlighting the flow in pink and with arrows. This is the situation where waste heat of the motor and inverter are being used to heat up the battery.
      Tesla thermal managent flow highlighted

    • And for the sake of completeness, this is the diagram showing separate loops.
      Tesla thermal managent separate loops flow highlighted
      In that case the battery not being heated by the motor and the Tesla thermal controller can decide to heat it with the battery heater, cool it with the chiller or do nothing (light blue loop). Diagram is showing the chiller in the loop, but valve (4) changes that to the heater.
      Motor and inverter are being cooled by the radiator (green loop).

    • And another addition. In my diagram I just show the battery pack as a whole and within that as a black box. Within the pack all 16 modules are connected in parallel. There are two 14 mm ID tubes (supply and return) and 2×16 (in case of a 85 kWh pack) module tubes (ID = 6 mm).

  9. Hi Lars, incredible work. Your blog posts are extremely useful!! I have a question for you.

    You mentioned that the battery heater is controlled by the junction box. Is that simply a contactor? There is no CAN control right? To use the heater, you can simply switch high voltage to it and it will operate at rated power?

    • Thanks!
      The Tesla Front High Voltage Junction Box (FHVJB) has a PWM in for the battery heater control. That PWM signal is used in the FHVJB to high voltage PWM the battery heater with a couple of mosfets.
      I’ve never finished testing, but that seems to be a 12V PWM signal. Others have found that 50 Hz and 20-30% duty triggers difference in heating behavior.

      • Thanks Lars that is interesting. So do you think it would be possible to use the Tesla battery heater without FHVJB? I am in the market for a battery heater and am looking for low-cost solutions without buying a brand new one from a manufacturer. Do you have any other tips or potential avenues?

        • Yes, in the end the Tesla battery heater just needs high voltage. Switching it on/off with a contactor just runs it at full power alle the time when it’s on. So then you need a proper thermal controller to prevent (local) overheating.

  10. Could you please share what fittings you’ve used for the expansion valve (6007362-00-C)?
    Also, do you by chance know the max pressure and temp that the a/c system is design for?
    I’m thinking of using the pwm version of the compressor and the battery chiller setup from Tesla. The rest of the a/c system to be custom.
    Thanks in advance.

    • The fittings for the Tesla chiller are not common and I could not find them off the shelve so I had them custom made.
      The system pressures depend on the trinary switch you use. I used one with the following switch points:
      Low pressure off (turn compressor off) = 2.0 Bar
      Middle pressure, fan On = 13.0 Bar
      Middle pressure, fan Off = 16.0 Bar
      High pressure on (turn compressor off) = 25.0 Bar
      High pressure off (compressor can be on again) = 19.0 Bar

  11. Could you please explain all the possible valve changes and loops for which the battery is heated or cooled, and could you give the dimensions of the battery cooling and heating components with the connections as I can’t seem to find the specifics anywhere for me to run a model? Thank You

    • Student assignments are great, but please do not expect that I will do your homework. There is a lot of information in the above blogpost which should give you a good head start doing further research and find the answers.
      As also written to Mithurjan by e-mail, for dimension and models I can recommend searching on Grabcad.

  12. Hi! Have you had any success launching the TMS Battery Heater?
    in my project, I will use this heater in conjunction with MS FHVJB. I already have these parts in stock, but I still haven’t been able to learn how to control them with an ARDUINO. Does anyone know what else could be the reason? maybe someone has a ready-made code?
    as for me, I have developed a code for arduino that I can share. it controls the PwM for the water pump using a PID regulator using external temperature sensors.


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