Troubleshooting Guide - Western UniMount MVP Mechanic's Manual

TROUBLESHOOTING GUIDE

Troubleshooting Guide Contents
General Diagnostic Table ............... 47
Packing Nut Adjustment ................ 50
Motor Test ...................................... 51
Motor and Motor Relay Test
Diagram ......................................... 52
Motor Relay Test ............................ 53
Vehicle Harness Test -
Motor Relay ................................... 54
Control Test ................................... 55
Pump Pressure Test ...................... 56
Solenoid Coil Activation Test .......... 57
Vehicle Harness Test -
Solenoid Coils ................................ 59
Hydraulic System Test ................... 60
Relief Valve Inspection and
Adjustment .................................... 63
Pilot Operated Check Valve
Inspection ...................................... 64
Individual Solenoid Coil Test .......... 64
Solenoid Cartridge Valve
Inspection ...................................... 65
Vehicle Headlamp Test .................. 66
Headlamp Test Diagram ................ 67
Plow Headlamp Test ...................... 68
Park/Turn Lamp Test ..................... 69
Lit. No. 21857
Introduction
This guide consists of a series of
tables, diagrams, flow charts and
other information. When used
properly it will assist the mechanic in
identifying and repairing faulty system
components. Western highly
recommends the use of the
MVP ® Electrical Tester as a
timesaving option for electrical
system diagnosis. When using this
tester, refer to the supplied instruction
manual for proper use of the tester.
Any malfunction of the MVP
snowplow can be categorized as
either mechanical, electrical or
hydraulic. Mechanical issues are
generally related to the blade wings,
A-frame, lift frame and mount
components and are usually identified
by visual inspection. Electrical and
hydraulic issues can be difficult to
trace to the component level and that
is the purpose of this troubleshooting
guide. Read and understand the
Theory of Operation before
attempting troubleshooting.
How to Use the Troubleshooting
Guide
Because of the relative complexity of
the MVP snowplow electrical and
hydraulic systems, many variables
need to be eliminated in order to
obtain workable test procedures.
These variables translate into
conditions listed before the tables or
flow charts and must be satisfied
before proceeding.
If the listed conditions are not met,
the procedure can result in inaccurate
results and wasted time.
In many cases, satisfying the listed
conditions alone will solve the
problem.
1. Go to the General Diagnostic
Table and satisfy the ten listed
conditions. These conditions
must be met before proceeding
into the table or to any
subsequent test.
2. Locate the condition in the table
which best describes the problem
and check possible causes and
actions in the order listed.
3. Proceed to a service procedure,
another condition, or a specific
test as directed. All tests except
the Hydraulic System Test use a
flow chart format. To use these
flow charts, first satisfy any listed
conditions at the top of the page.
Then begin at the upper left
square and proceed as directed.
4. Follow along sequentially through
the table and tests, referring to
the hydraulic and electrical
schematics in the Theory of
Operation section and the
component Identification and
Location diagrams. Eventually
the problem will be pinpointed at
the component level.
Electrical Testing
Read and understand the section
describing electrical circuit operation
in the Theory of Operation section. A
simple 12V test light with a ground
lead can be used for circuit testing.
When directed to check for 12 volts
(12V), ground the test lamp lead and
probe the terminal. When asked to
check for ground, attach the test lamp
lead to +12V and probe the terminal.
Note that 12V is a nominal value. If
using a voltmeter, actual voltage will
vary with the vehicle and presence of
loads in tested circuits.
June 15, 2003
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