Tesla Model 3 Drive Unit PCB Install

Introduction

This document outlines the step-by-step procedure for installing a Tesla Model 3 Drive Unit PCB in a Tesla Model 3. Please follow these instructions carefully to ensure a successful installation. The information here is derived from Damien Maguire's installation video and V3.2 update.

Note: This guide applies to the V3.2 PCB as shipped from the EV BMW Web Shop.

Tools Required

Electronics Assembly Tools

• Soldering iron
• Solder
• Gel flux such as Kingbo RMA-218
• Desoldering braid
• Vacuum desoldering gun
  • 320°C
  • 0.8 mm desoldering nozzle
• Blow torch or 250W soldering iron

Hand Tools

• Tweezers
• Magnifying glass
• Torx T10 screwdriver
• Torx T20 screwdriver
• Small flat bladed screwdriver
• Side cutters

Commissioning Tools

• Bench PSU capable of supplying 12V
• USB CAN adapter with OpenInverter CAN Tool OR ESP32 CAN interface with esp32-web-interface can firmware
• Multimeter
• 48V DC power supply OR battery with current limiting heating element or incandescent light bulb
• Dual channel throttle pedal (e.g. BMW E36 throttle pedal)
• Momentary switch
• SPST changeover switch

Remove OEM PCB from the Inverter Housing

parts/ connections to salvage/ unsolder

1. Remove unnecessary hardware from the housing:
   • Remove the coolant connectors from the housing to allow it to sit flat on the workbench.
   • Remove the gasket around the edge of the housing carefully to avoid damaging it.
2. Identify the 3 groups of components to be desoldered:
   • The red rectangles indicate the power transistors
     • Some drive units only have 3 of the 4 transistors fitted
   • The red circles indicate the main DC bus capacitor
   • The yellow circles indicate the HV interlock connections on the main DC connector
3. Apply a small amount of flux to each joint to be removed
4. Apply the desoldering gun and allow it to heat the joint fully. Wiggle it gently before applying the vacuum.
   • Try to hold the desoldering gun perpendicular to the PCB to ensure a good vacuum
   • Additional heat from a soldering iron may help
5. Use tweezers to wiggle each pin to verify it is free
   • If a pin is not free try the desoldering gun again
   • If problems persist, resolder the joint and try again
   • Be careful not to apply heat from the soldering iron or desolder gun for extended periods otherwise you might lift a pad on the PCB
6. Once a pin is free move on to the next pin and repeat the process from step 3
7. Carefully check that all the pins are loose with tweezers
8. Unscrew the 11 screws securing the PCB to the housing using the Torx T20 screwdriver.
9. Unclip the 30-way low-voltage connector clip
   • Insert a flat bladed screwdriver vertically
   • Squeeze towards the center of the connector whilst lifting
10. Carefully lift up the PCB
    • If it requires force to lift the PCB, carefully review the desoldering and mounting screws
11. Flip the PCB over and use a pair of side cutters to lift but not cut the black plastic clips holding the insulating shield to the underside of the PCB
    • Save the insulating shield for later with the replacement PCB
    • Save as many of the clips as they will also be required later

Remove Current Sensor Block

The black current sensor block is located on the underside of the PCB. It needs to be preserved to fit to the replacement PCB.

1. Unscrew the 3 screws securing the current sensor block using the Torx T10 screwdriver
   • Boards fitted with pyrofuses will have 2 T10 screws.
2. Release the 4 plastic clips in the centre of the sensor block
3. Apply fresh solder and flux to all 4 pins on each current sensor
   • Aim to bridge all 4 pins
   • The process will emit some smoke as it burns off the conformal coating
4. Insert the flat bladed screwdriver gently between the plastic housing and the PCB
5. Apply heat with a soldering iron to one of the current sensors while levering the housing to release it
   • The current sensors are bonded with heat sensitive glue into the current sensor housing. Be careful not to apply a lot of force.
   • Once the leads start moving move to the next sensor
   • Move back and forth between the sensors until the whole assembly has been removed
   • The two sensors should remain soldered to the PCB

Remove 30-pin Low-Voltage Connector

1. Clamp the plastic holder on the bottom of the array of pins that make up the low-voltage connector in a vice
2. Hold the PCB firmly by the far edge and apply a lifting force
3. Apply a blow torch quickly to the 30 solder connections and move back and forth quickly
   • Watch the video demonstration
4. As the solder melts quickly lift the PCB and torch away
   • The key to success is to use a lot of heat but for a very short time
   • At this point the Tesla PCB is sacrificed to obtain the connector pin array. There is no known source for connector at this point.

Alternate Technique

• As above but use a 250W soldering iron and fresh solder

Initial Power Up Testing

Before attempting to install the PCB on the inverter chassis it is important to test the assembly on the bench. This allows faults from the assembly process to be rectified more simply.

First Power On

1. Connect 12V power temporarily to the board using dupont cables and a bench PSU
   • Pin 22 - Unswitched +12V
   • Pin 3 - Switched +12V
   • Top left mounting hole - Ground
2. Connect a CAN interface
   • Pin 12 - CANH
   • Pin 2 - CANL
3. Identify the 3 indicator LEDs on the board:
   • D7 3V3 ACTIVE - Located top right of the board
   • D18 - Located above the MCU
   • D58 GATE FAULT - Located on the left edge of the board next to the USA/IE flag
4. Set the current limit on the bench PSU to 500mA
5. Turn on the PSU and check the LED
   • 3V3 ACTIVE LED should be permanently lit
   • D18 should light for 1 second then start flashing at 2Hz
   • GATE FAULT should flash once and then remain off
6. Verify current consumption is around 300mA

Verify Status

It is important to check that the components we have fitted are working correctly while the board is still easy to work on.

1. Using the CAN configuration tool check the errors list
   • There should be two errors: HIRESOFS and OILPUMPFAULT
   • More errors indicate that trouble shooting is required
2. Set the multimeter to DC volts and check the following test points:

Black Lead	Red Lead	Expected Voltage	Description
TP7	TP8	12.1 V	High-side phase A gate drive positive supply
TP7	TP6	-5.1 V	High-side phase A gate drive negative supply
TP10	TP9	12.1 V	High-side phase C gate drive positive supply
TP10	TP11	-5.1 V	High-side phase C gate drive negative supply
TP13	TP12	12.1 V	High-side phase B gate drive positive supply
TP13	TP14	-5.1 V	High-side phase B gate drive negative supply
TP18	TP17	18.2 V	Low-side phase A gate drive positive supply
TP18	TP16	18.2 V	Low-side phase C gate drive positive supply
TP18	TP15	18.2 V	Low-side phase B gate drive positive supply

Troubleshooting

If the GATE FAULT LED is lit look at the m3_phaseX_xx Spot Values for clues:

• RxCRC indicates a communications problem between the MCU and the gate driver ICs. All 6 chips have to be working to correctly initialise. Check the orientation and soldering on the upper side of all 6 gate driver ICs.
• Any fault values reported on the m3_phaseX_xx Spot Values should point to the affected gate driver IC
• Check the soldering on the gate drive IC and for any dislodged passive components near the affected IC
• The gate drive supply voltages should be identical to each other and very close the values in the table. The power supplies are current limited so any problems should not damage parts but need to be fixed before proceeding.

Current Sensor Block Installation

1. The current sensors are fitted to the underside of the PCB and protected by a plastic block for shipping
2. Cut the cable ties holding the protection blocks in place and remove them
3. Clip the black plastic current sensor block housing over the sensor ICs
4. Flip the board back over to the component side
5. Screw in the 3 Torx T10 mounting screws

Main 30-pin Connector Fitting

1. Clamp the 30-pin connector array
2. Use solder braid and some flux to clean all the excess solder from all pins
3. Insert the connector into the PCB
4. Tack two corner pins with solder
5. Flip the board over and ensure that plastic mount on the connector is flush with the board
   • It is critical that the connector is mounted flush otherwise the mating connector on the wiring harness will not engage cleanly
6. Solder all of the remaining pins

Fitting the PCB to the Inverter Chassis

Preparing the PCB

1. The PCB is supplied with 3 thermistor temperature sensors
2. Insert each thermistor into the underside of the PCB
   • Don't solder the thermistors at this stage, just bend the leads to hold them in place
3. Place the insulation shield recovered from the Tesla PCB over the underside of the board
4. Fit the shield using the 6 plastic clips from the Tesla PCB
5. Optional: Fit the WiFi/Terminal header and SWD Prog headers if desired
   • WiFi control boards will not fit or function within the inverter when fitted to the motor but can be useful for bench testing

Fitting the PCB to the Chassis

1. Place the main inverter chassis on the bench
2. Lower the PCB onto the chassis in roughly the following order
   1. HVIL pins at the top of the board
   2. Locating dowel in the top-right of the board
   3. 4 DC bus capacitor pins in the middle of the board
   4. Main MOSFET pins
   5. Locating dowel in the bottom-left of the board
   • Tap gently and be careful not to apply any significant pressure
   • MOSFET pins may require gentle tweaking to get the alignment correct
3. Check with a finger that pins are through the board
   • Each MOSFET position has two pins (labelled S and G)
   • There are two HVIL pins (labelled CONN1)
   • There are 4 DC bus capacitor pins (labelled E12, E13, E14 and E15)
4. Screw in each of the T20 fasteners to the PCB
   • V3.2 PCB only : Don't fit a screw in H10 as the hole is in the wrong place
   • Hole alignment is improving with each board revision. A little jiggling from side to side may be required to get all fasteners to fit.

Soldering the Chassis Components

1. Lift the inverter chassis to be able to look into the side
2. Push the leads of thermistor ST1 down into the thermal compound on the chassis
3. Solder the leads on the thermistor
4. Repeat for thermistors ST2 and ST3 in between the MOSFETs
5. Solder the 4 DC bus capacitor pins E12, E13, E14 and E15
6. Recheck each of the MOSFET pins are visible through the PCB before starting to solder
   • Some inverters have only 3 pairs of MOSFETs for each phase others 4
7. Solder each MOSFET pin
   • Be careful when soldering not to keep the iron on the pin for too long. If heat is applied for too long the solder, assisted by gravity, can wick down the pins into the bus bars on the chassis and cause shorts.
8. Fit the plastic clip over the top of the 30-pin main connector

Bench Testing the Motor

Low Voltage Testing

1. Place the inverter on a suitable work surface next to the motor
2. Connect the wiring harness to:
   • Inverter, oil pump and resolver on the motor
   • 12V power supply
   • CAN configuration tool
3. Turn on the 12V PSU
4. Confirm:
   • The LEDs behave the same way as the original power on test
   • The CAN configuration tool should now show no errors
   • The oil pump will be running continuously
   • It may be possible to hear the 8.8kHz resolver exciter tone

Spinning the Motor

1. Check the following inverter parameters:
   • throtcur = 1
   • brakeregen = 0 (disabling regen is critical when using a DC power supply to avoid inverter and PSU damage)
   • offthrotregen = 0
2. Connect the following:
   • Momentary switch to the Start input and 12V
   • Changeover switch to the Forward and Reverse inputs and 12V positive
   • Throttle pedal to the two inputs
3. Connect the 3 phases on the inverter to the motor
   • Short equal lengths of 10mm^2 cable should be sufficient
4. Connect the PSU or battery to the inverter
   • The positive connection on the inverter is the one nearest the 30-pin low voltage connector
   • If using a battery use an incandescent light bulb or heating element as a pre-charge and current limiter
5. Press the Start button
   • Verify that the inverter goes into Run mode
6. Select forward
7. Depress the throttle pedal
8. Observe the motor spinning!