30Service Manual – SC900 24 - Electrical System
Troubleshooting
The SC900 machine architecture is based on a hybrid of “Relay Logic” with limited control logic from the
Curtis Drive Controller. This causes a lot of the system troubleshooting to be interrelated between the
standard relay-logic components and the drive system controller. Most of the troubleshooting scenarios will
be listed here, unless they are specic solely to the drive controller.
Problem Cause Notes & Correction
No system function.
• No Drive
• No Brush
• No Vac
• No Hour Meter LED
Main 150A fuse is
blown
This is almost the equivalent of disconnecting the main
battery connector, except that the optional onboard battery
charger would also show as not being connected.
• If the optional charger indicates that the battery is present,
then this is not the cause.
• Replace the 150A fuse module on the positive battery
terminal.
KSI circuit is disabled The KSI circuit is the equivalent of not turning the key switch
on, but can have a couple of different causes. The most
notable symptom is that the hour meter indicators will not
illuminate, nor will the vacuum run.
• If the vacuum motor runs, then this is not the problem.
• Reset the 2.5A circuit breaker
• If the onboard charger is present, make sure the interlock
wire is connected to the 2.5A breaker.
• If the onboard charger is not present, make sure the red
battery wire is connected to the 2.5A breaker.
• If the optional TrackClean module is not installed, make
sure the shunt connector is in place.
• Check for 36 Volts at pin-5 of the Curtis controller. If not
present, work back upstream to locate the break.
Limited System
Function
• No Drive
• No Scrub
• But Vacuum Runs
Drive Controller Fault
Because the vacuum runs, this is most likely related to a
drive controller fault. There can be many causes to a drive
controller fault. Refer to the Drive Controller “Troubleshooting”
on page 18. Two exceptions that would not be error code
drive:
• A break in the KSI input directly at the drive controller
• Open circuit for the Go switches
No Drive, but all other
systems functional
• No Drive
• Brush active
• Vacuum active
Drive motor or throttle
fault.
This condition indicates that the drive controller has activated
the brake release, but is not driving the transaxle without a
drive controller fault. The most likely cause is a speed limit
fault.
• Because the scrub system is functional, it is known that the
Go switches are functional.
• The most likely cause is a broken speed limit pot wiper wire
connection. The drive is active, but at zero speed.
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