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.

Tools Required

• Soldering iron
• Solder
• Gel flux such as Kingbo RMA-218
• Vacuum desoldering gun
  • 320°C
  • 0.8 mm desoldering nozzle
• Blow torch or 250W soldering iron
• Tweezers
• Magnifying glass
• Torx T10 screwdriver
• Torx T20 screwdriver
• Small flat bladed screwdriver
• Bench PSU capable of supplying 12V
• USB CAN adapter with OpenInverter CAN Tool OR ESP32 CAN interface with esp32-web-interface can firmware
• Multimeter

Fit missing components to the replacement PCB - Beta Version only

If you are using a Beta version of the replacement PCB, you will need to fit some missing components before installation. These will be supplied in a bag with the board.

Components To Fit

• U5 - ACPL-M49T-000E - Located in top right (Buffalo, New York)
• U33 - ACPL-M49T-000E - Located in the upper centre (Chicago, Illinois)
• Q983, Q43, Q982, Q42, Q981, Q41 - STD45P4LLF6 - Located across the lower part of the board

Fitting Notes

• Apply gel flux to the pads before soldering.
• Use a magnifying glass to ensure proper alignment of the two optocouplers (U5 and U33). The circle indicator on the component should match the bar on silkscreen that indicates pin 1
• When soldering the transistors solder the small pins first to hold them in place, then solder the larger tab last. You may find heavier gauge solder useful for the tab. Apply heat to the tab and allow capillary action to draw solder under the tab.

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 gentle 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 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 review 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 lov-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 remove the black plastic clips holding the insulating shield to the underside of the PCB
    • Save the insulating shield for later with the replacement PCB

Recover gate drive components from the Tesla PCB (Optional)

Remove Gate Driver Transformer

1. Apply some flux to all of the legs of the gate driver power supply transformer
2. Slip a flat bladed screwdriver under the edge of the transformer and use its weight to apply a small amount of pressure
3. Use a hot air gun to apply a lot of heat to the legs on one side of the transformer
4. As the heat gun melts the conformal coating and solder gently lift up the leg
5. Move up the side of the transformer
6. Repeat on the other side

Remove Gate Driver Chips

1. Apply some flux to all the pins on each gate driver chip U303, U293, U302, U292, U301 and U291
2. Place a scalpel under the edge of the first chip
3. Use a heat gun to desolder the chip
4. As the solder melts it will be possible to lift the chip with the scalpel
   • The conformal coating means the chip will not lift as easily as a regular PCB. Only a tiny amount of force will be required to break the adhesion though.

Remove current sensor

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 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
6. Desolder each current sensor by apply some flux and hot air
   • Use tweezers to gently work the sensors free from the board

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
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

Assemble Recovered Components to the PCB

Purchasable Components

The following components can be purchased new and do not need to be recovered:

• Gate drive transformer : TDK VGT22EPC-200S6A12
• Gate driver IC : STGAP1BSTR

Install Gate Drive Transformer

1. Remove the additional framing left around the PCB to protect it in shipping
2. Apply some flux to the gate drive transformer pads
3. Orient the transformer to match the footprint
4. Tack one leg of the transformer to secure it before soldering the other pins

Install Gate Driver ICs

1. Orient the first gate driver IC with the dimple indicating pin 1 with the small arrow in the top right corner of the footprint
2. Tack opposite corners of the IC
3. Use standard SMD drag soldering technique to solder each pin
4. Inspect the board using a magnifier or microscope
   • Be careful to avoid shorts between pins - these can be cleaned up with desoldering braid
   • Access on the lower side of the chips nearest to the bottom of the board is limited. Be careful to avoid dislodging the many small passive components around the IC.

Fit DC-DC Converter - Beta Version only

1. Insert the DC-DC converter and tack one pin
2. Ensure there is some pressure on the top of the DC-DC converter
3. Reflow the tacked pin to ensure the DC-DC converter is flush to the board
   • This is important to avoid fatigue of the converter pins
4. Finish soldering all the remaining pins

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 four errors: HIRESOFS, HICUROFS1, HICUROFS2 and OILPUMPFAULT
   • More errors indicates 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 Installation

The current sensor ICs (U30 and U40) MLX91209LVA-CAA-002-SP can be purchased new or recovered from the original Tesla PCB.

1. The current sensors are fitted to the underside of the PCB so flip the board onto the component side
2. Orient the sensor with the chamfer towards the edge of the board, away from the rectangular hole for the phase conductor
3. Push the current sensor until it sits flush with the board
4. Flip the board back to site component side up
5. Clip the black plastic current sensor housing back over the sensor ICs
6. Push the leads of each of the current sensors down into the current sensor block
7. Apply some flux and tack one pin of each sensor
   • Do not cut the leads of the sensor at this point
8. Unclip the current sensor block and check the height of the sensor ICs above the PCB
   • There should be 4.7mm of exposed lead between the PCB and the black plastic of the sensor
9. Reclip the current sensor block over the ICs
10. Solder all of the remaining leads and cut the excess lead from the sensor IC wires
11. Screw in the 3 Torx T10 mounting screws
    • Beta boards only: Do not fit the left hand screw as it will damage R127 and C23 and potentially short a circuit trace

Verify Current Sensors

1. Reattach the power supply to the board
2. Power up the board again
3. The power, activity and gate fault LEDs should behave as on first power up
4. Using the multimeter on DC Volts check between ground (H7) and TP22 (marked IL1)
   • The test points are located on the left hand edge of the board next to the GATE FAULT LED
   • The voltage should read 1.56 volts
5. Repeat for TP23 (IL2) which should read the same value
6. Optionally check the error list in your CAN configuration tool. The HICUROFS1 and HICUROFS2 errors should now not be present.

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 Telsa 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 but don't 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
   • Beta boards 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.