Fisher HT Series - Troubleshooting: Control, Cable, and Module; Diagnosing Control or Module Issues

Lit. No. 41298, Rev. 01 February 15, 2019
63
TROUBLESHOOTING
CAUTION
Circuit board may be damaged by static
electricity. Always touch ground before
handling PC board.
To Safely Handle PC Board:
Before disassembling control and touching the PC
board, be sure to remove any static charge from
yourself. Static charge can build up as a technician
works on the control. Best practice is to work at a
properly grounded work station with a grounded
wrist strap attached to the technician. In place of
proper work station, the technician should work
in an oil and solvent free area and touch a good
ground each time before touching the PC board
while servicing the unit.
Handle the PC board by the edges only.
Do not touch the carbon (black) areas of the
keypad. Your skin oils will deteriorate the contact
area.
CONTROL/CABLE/PLOW MODULE TEST
CONDITION POSSIBLE CAUSE
CORRECTIVE ACTION
Control power
light is not
ON.
Snowplow is not connected.
Make sure grille plugs between snowplow and truck are
properly connected.
Incomplete harness connection(s) or
damaged harness(es).
With the vehicle switched accessory ON, test the 4-pin
connector inside the cab. If pin 1 does not have 12V and/or
if pin 4 does not have ground, use the electrical schematic in
this guide to trace the wires from the connector back to their
source. Look for incomplete connections or damaged wires.
Complete connections or repair/replace damaged wires and
harnesses as needed.
Single-pin connector on vehicle plow
lighting harness is not connected.
Make sure single-pin connector on vehicle plow lighting
harness is properly connected.
Harnesses connected to Isolation
Module incorrectly.
Using the electrical schematic in this guide, verify that
Isolation Module and harnesses are properly connected.
Control fuse is blown. Replace all blown fuses in under-hood electrical harnesses.
Control
power light is
blinking (slow
fl ash).
Poor connection between control and
module, damaged control, or damaged
Plow Module.
Make sure all plugs (control, between the snowplow and
truck, on the snowplow, etc.) are properly connected.
Check continuity of twisted pair wiring between control
connector and Plow Module connector.
If all plugs are properly connected, install a properly working
control. If problem is corrected, replace PC board and/or
coiled cord in damaged control.
If problem is not corrected with properly working control,
replace Plow Module.
Control
power light is
blinking (fast).
Snowplow is locked. Enter 4-digit security code to unlock snowplow.
Control power
light is ON,
but snowplow
does not
respond.
Harnesses connected to Isolation
Module incorrectly.
Using the electrical schematic in this guide, verify that
Isolation Module harnesses are properly connected.
Blown fuse or damaged Plow Module.
Replace all blown fuses on truck and snowplow.
If fuses are all okay, check for 12V at all coils and primary
terminal of motor relay. If 12V is missing from any coil or
relay, replace Plow Module. If 12V is present, go to next
Possible Cause.
Damaged harness(es) or cable(s).
Perform a Solenoid Coil Activation Test (SCAT) according to
the instructions in this guide. Replace/repair any damaged
harnesses and cables.
Damaged control or Plow Module.
Install a properly working control. If problem is corrected,
replace PC board and/or coiled cord in damaged control.
If problem is not corrected with properly working control,
replace Plow Module.