TROUBLESHOOTING GUIDE (TEST WITHOUT TRAILER FIRST):
No trailer connected
CONDITION DISPLAY PROBABLE CAUSE POSSIBLE SOLUTION
Decimal point does not light Blank No power to control, no
ground, reversed black and
white wires
Check brake control
wiring
Decimal point on after 12 – 15
minutes of inactivity
Decimal Red wire connected to
wrong side of stoplight
switch or to wrong wire
Check brake control
wiring
Display shows output power
when brake pedal is pushed or
manual control is actuated
Output Power
Not blinking
Brake control unit mis-
wired or contamination in
trailer plug socket
Check brake control
wiring, clean and dry
trailer plug
Display shows L.b
Can also happen with trailer
connected
Tow vehicle’s system
voltage low
Check tow vehicle’s
battery and charging
system
Display shows E.1. when
manual control is applied
Red wire connected to
ground side of stoplight
switch or is shorted to
ground
Check brake control wir-
ing, may require change
to switch setting. See
"manual control" section
Display shows OL when brake
pedal or manual override
is used
Blinking Short in blue wire output
circuit or trailer plug
Locate and correct short
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