Troubleshooting Procedures

This guide provides step-by-step procedures to troubleshoot ASI BAC motor controllers and facilitate warranty claims. It covers low power controllers (BAC355, BAC555, BAC855) and is generalized for various applications.

Required Tools

Before beginning troubleshooting, gather the following equipment:

Tool	Purpose
Safety glasses	Eye protection
ESD mat	Static discharge protection
Current-limited power supply (up to 48V)	Safe power delivery
Digital multimeter	Voltage, resistance, capacitance measurements
ASI evaluation harness	Controller connection
PC BACDoor + USB isolator	Serial communication
BACDoor Mobile app	Bluetooth testing (if applicable)
Wire stripper and electrical tape	Wire preparation
PEAK CAN dongle + PCAN viewer	CAN communication (if applicable)

Critical Safety Warning

DO NOT provide power to the controller until instructed by this guide
DO NOT connect a motor to the controller during troubleshooting
When stripping wires, isolate from other wires and connection points

Wiring Reference

Control Connector Pinout

Pin	Color	Function
1	Black	Hall GND
2	White/Black	Hall 5V Out
3	Green	Hall-A
4	Blue	Hall-C
5	Black	GND
6	Yellow	Hall-B
7	Purple/White	ABMS
8	Orange/White	Brake 2
9	Blue/Black	PFS
10	Orange	Brake 1
11	Red/White	5V Output
12	Blue/White	Cruise
13	Brown	12V Output
14	Purple	Throttle
15	Purple/Black	HDQ
16	Black	GND
17	Grey/White	TTL-RX
18	Yellow/White	TTL-TX
19	Grey/Black	CAN-L
20	Yellow/Black	CAN-H
21	Red	B+ Out
22	White	Key-in
23	Green/White	6V Light
24	Black	Light ground

Step 1: Visual Inspection

Before electrical testing, perform a thorough visual inspection.

Record Controller Information

Document the following from the controller label:

Model Number
Part Number
Hardware Number
Firmware Number
Parameter File Number
Revision
Serial Number
Country of Origin

Document the Issue

Record the nature of the issue with as much detail as possible:

When does the problem occur?
Is it intermittent or constant?
What were the conditions when it started?
Have any recent changes been made?

Physical Inspection

Examine the controller thoroughly for:

Cracks in the housing
Burns or discoloration
Damage to connectors
LED indicator condition
Any other visible defects

Step 2: Short Circuit Check

Use the resistance function on your multimeter to verify no internal shorts exist.

Resistance Tests

Perform these measurements and record results:

Test	Probes	Expected Result
Battery+ to Battery-	+ to + terminal, - to - terminal	>5000Ω
Heatsink to Battery-	Heatsink to - terminal	>5000Ω
Battery+ to Hall GND	+ terminal to Pin 1	>5000Ω
Battery+ to Light GND	+ terminal to Pin 24	>5000Ω
Battery+ to Control GND	+ terminal to Pin 5/16	>5000Ω
Battery- to Phase U	- terminal to Phase U	>5000Ω
Battery- to Phase V	- terminal to Phase V	>5000Ω
Battery- to Phase W	- terminal to Phase W	>5000Ω
Battery+ to Phase U	+ terminal to Phase U	>5000Ω
Battery+ to Phase V	+ terminal to Phase V	>5000Ω
Battery+ to Phase W	+ terminal to Phase W	>5000Ω

Low Resistance

Any reading below 5000Ω indicates a potential short circuit. Do not proceed with power-up testing.

Capacitance Test (Optional)

If your multimeter has capacitance function:

Measure between Battery+ and Battery- terminals
Record the capacitance value

Only proceed if all resistance tests pass.

Step 3: Power-Up Test

Connect and power the controller using a current-limited supply.

Connect Power Supply

Connect Battery+ and Battery- terminals to a 48V current-limited power supply set to 250mA limit.

Check B+ Out Pin

Measure voltage at the B+ Out pin (Pin 21) with respect to ground.

Voltage Reading	Meaning
0V	Hardware damaged - try Key-in bypass
Same as supply	Normal - proceed to Key-in

Key-In Connection

If B+ Out shows supply voltage, short the Key-in pin (Pin 22) to B+ Out. Keep connected during testing.

Power On

Turn on the power supply and observe current draw.

Overcurrent

If power supply maxes out current limit, immediately stop the test.

Check LED

Observe the LED indicator and record:

ON (solid)
OFF
Blinking pattern (e.g., "3-1" = 3 blinks, pause, 1 blink, long pause)

Refer to Faults and Warnings for flash code meanings.

Step 4: Communication Test

Establish communication with the controller.

TTL Connection

Connect USB Isolator

Connect controller to computer through USB isolator.

TX/RX Crossover

Connect controller TTL TX to computer RX and vice versa.

Open BACDoor

Launch PC BACDoor software.

Configure Connection

Set connection parameters:

Baud rate: 115200 (ASI default)
Address: 1

Alternative Baud Rates

If connection fails at 115200, try:

9600
Other available options

Record which baud rate works.

CAN Connection

If using CAN-compatible controller:

Use baud rate 250kbps and address 42 (ASI defaults)
Connect PEAK CAN dongle through USB isolator
Use appropriate settings if previously configured differently

Bluetooth Connection (if applicable)

Verify controller part number includes "BT"
Enable Bluetooth on mobile device
Look for "e-Bike" or "ASI devices" in BACDoor Mobile
Place phone close to controller and refresh

Unresponsive Controller Recovery

If the controller doesn't respond (LED off, no communication):

Download Recovery Tool

Download C2Prog (v1.8).

Connect

Select the COM port connected to the controller.

Load Firmware

Load the firmware image (.ehx file).

Program

Click Program.

Power Cycle

Power cycle the controller.

If still unresponsive, stop testing - controller requires return for service.

Step 5: Record Controller Status

Once connected, document the controller state.

Version Information

Record from BACDoor:

Firmware version
Build version
Variant
Bootloader version
OTP Serial number

Save Parameters

Use Save to File (not Save to File 512 or 256) to capture all parameters.

Check Fault Status

If status indicator is red, hover cursor to read fault
Navigate to Features/Faults tab
Check Faults, Faults2, Warnings, Warnings2
Record any bits set to 1

Record OTP Serial Numbers

Navigate to Controller Debug/OPT/CRC/Version tab and record:

OTP serial number 0
OTP serial number 1

Step 6: Peripheral Verification

Test all peripheral outputs and inputs.

Voltage Outputs

Measure these outputs with multimeter:

Output	Pin	Expected Voltage
12V Output	13	~12V
5V Output	11	~5V
6V Light Output	23	~6V
Hall 5V Output	2	~5V

Floating Input Voltages

Measure floating voltages (not connected to anything):

Input	Pin	Typical Range
Hall A	3	~5V (pulled up)
Hall B	6	~5V (pulled up)
Hall C	4	~5V (pulled up)
Cruise	12	~5V (pulled up)
PFS	9	~5V (pulled up)
Brake 1	10	~5V (pulled up)
Brake 2	8	~5V (pulled up)

Digital Input Testing

In BACDoor, observe the digital inputs bit vector:

Test	Action	Expected Result
Hall C	Connect to Hall GND	Bit 0 = 1
Hall B	Connect to Hall GND	Bit 1 = 1
Hall A	Connect to Hall GND	Bit 2 = 1
PFS	Connect to GND	Bit 3 = 1
Cruise	Connect to GND	Bit 4 = 1

Bits should toggle to 1 when connected to ground.

Analog Input Testing

In BACDoor, verify analog inputs respond:

Test	Action	Expected
Throttle	Read voltage	Record baseline
Throttle	Connect to 5V	Voltage increases
Brake 1	Read voltage	Record baseline
Brake 1	Connect to GND	Voltage decreases
Brake 2	Read voltage	Record baseline
Brake 2	Connect to GND	Voltage decreases
ABMS	Read voltage	Record baseline
ABMS	Connect to 5V	Voltage increases

Switchable Output Testing

Test the 6V switchable output:

In BACDoor, write 1 to Remote digital commands bit 1
Measure 6V output with multimeter
Write 0 to turn off
Verify output turns off

Low-Side Switch Testing

Test HDQ low-side switch:

Write 1 to Remote digital commands bit 9
Measure resistance between HDQ pin and ground (should be low)
Write 0 to turn off
Resistance should return to high

Step 7: CAN Bus Testing

For CAN-compatible controllers, verify CAN communication.

Termination Check

Ensure both ends of CAN bus have 120Ω termination resistors
Measure resistance between CAN-H and CAN-L (disconnected from devices)
Expected: ~60Ω (two 120Ω in parallel)

Use Communications Configuration Vector bit 12 to enable software termination if needed.

TPDO Configuration

Ensure TPDOs are configured to send periodic messages:

Navigate to CAN TPDO1,2 tab and configure:

TPDO enabled
Appropriate transmission interval
Save to flash

PCAN Viewer Test

Connect PEAK CAN dongle (with USB isolator)
Open PCAN Viewer
Set baud rate to match controller configuration
Record:
- Address showing data
- Data content

No Data Troubleshooting

If no data appears:

Verify termination resistor configuration
Check TPDO setup
Verify baud rate matches

Step 8: POST Testing

Power-On Self Test verifies phase hardware.

Record Current Sensor Offsets

In BACDoor, record:

Phase A current sensor offset
Phase C current sensor offset

Record Phase Voltages and Currents

Record displayed values for:

Phase U/A, V/B, W/C voltages
Phase U/A, V/B, W/C currents

POST Parameters

Start polling these parameters:

Parameter	Description
Motor phase U/A low voltage POST	Phase U low voltage test
Motor phase V/B low voltage POST	Phase V low voltage test
Motor phase W/C low voltage POST	Phase W low voltage test
Motor phase U/A open circuit voltage POST	Phase U open test
Motor phase V/B open circuit voltage POST	Phase V open test
Motor phase W/C open circuit voltage POST	Phase W open test
Motor phase U/A high voltage POST	Phase U high voltage test
Motor phase V/B high voltage POST	Phase V high voltage test
Motor phase W/C high voltage POST	Phase W high voltage test