Pro-150 Fault Finding Guide

We’ve written this guide to help customers diagnose and fix problems that may occur with the Pro-150. We don’t release complete circuit diagrams for current models but we hope this guide will shed some light on the important sections. If you have any questions not covered here, please let us know and we’ll do our best to update it. It may be useful to use this troubleshooting voltage table in conjunction with the information in this guide.

The power up sequence is that the 12v PSU is fed initially via D9, this feeds the 5v supply which powers the processor. Once the processor is running it senses the ignition switch state, then does a number of self-tests which include charging and discharging the main capacitors using the relays, and also checking for mosfets faults. If the self-tests are passed, relay RL4 operates which connects B+ through to the motor terminals, mosfets, and direction relays. The following diagrams show the circuit diagrams and the physical locations of the relevant sections.

Pro-150 fault finding



Fault code 05

Causes of fault code 05 that are internal to the controller are:

One or more main mosfets are short circuit. Measure the resistance between points A & B, then B & C in the picture. Expected values are 2MΩ – 4MΩ, damaged mosfets will show as 1Ω – 30Ω. If the mosfets are blown also check the 10Ω gate drive resistors. Short circuit mosftets can also cause the pre-charge resistors to burn, particularly at 48v.

Check the black plastic washers at D are present, these insulate the heatsink from the PCB.

Measure pre-charge resistance as shown. Check that Q16 is not short circuit.


Pro-150 relay driver


Pro-150 mosfet test