This page is an expanded version of the free fault finding page. Additional information will be added here as the need arises.
Common faults on the NCC series are - not common. So a full fault finding chart is not a practical proposition. But there are a few faults which occur, mainly because the 'bare board' style of the controller makes it susceptible to certain abuses.
You will probably need to identify the issue number of the controller.
See NCC series controllers, key components to identify the zener.
Does the reversing switch have any effect?
Reverse switch has no effect
I.e. the controller goes in the same direction whether or not you operate the reverse switch. In this case then the switch itself, or the wiring to it, is faulty. The reversing switch should apply battery voltage (from pin A) to pin C. When the switch is open, Pin C should have no voltage present on it.
If there is no voltage here regardless of the switch - trace back the wiring through the reverse switch to find the reason.
If there is full battery voltage present, regardless of the switch, then either
Reverse switch works, but controller is dead in one direction.
Here, the reverse switch has an effect - probably the controller is dead in one direction. If the reverse switch has an effect, then it's working and some signal is getting through.
As you advance the controller from zero speed, one relay should click in forward direction and the other relay should click if reverse is selected.
Note: the controller will not reverse properly if the output is open circuit: it requires some sort of load (resistor or motor) or the highside current limit engages and prevents correct operation.
Usually this means the controller is working but the gain is set too low. On a standard controller, reverse is at half of forward speed. If the gain is set low, forward speed is low and half of this low forward speed may not be enough tom get the motor moving.
Another theoretical possibility is that there the relay contacts are dirty. However these relays used do have high contact pressure and tend to be self cleaning as a bad contact will, initially, get hot - which clears the problem before it shows up.
The main capacitor can hold charge for more than an hour when the NCC is disconnected from the battery, so this can happen even when you think the system is dead.
Usually such welding is minor and a sharp tap, with a screwdriver handle, on the cover of the affected relay is sufficient to release the weld.
This would imply that there is a fault in the reversing switch or the reversing logic on the board.
You do have a motor connected, don't you? The regen current limit gets confused if there is no motor and stops the demand speed going to zero. To some extent commutation of current from drive to regen depends on the motor's inductance.
The action of the dual ramp reversing is explained in the circuit dual ramp description.
If the dual ramp reversing 'latches' with the controller at zero speed, there are two possibilities:
Half speed reverse will not disengage
Sorry about this - you've spotted a manufacturing defect. We don't make many, but we are only human! The half speed reverse must disengage if the link is properly broken. It follows that removing the header is not breaking the link. So look for a solder bridge across the appropriate pins.