TROUBLESHOOTING AND ELECTRICAL SYSTEM:
DIESEL VEHICLES
Test Procedures
12
DIODE TROUBLESHOOTING GUIDE
DIODE
IN-LINE WIRE
LOCATION
(WIRES)
FUNCTION
FAILURE
CONDITION
SYMPTOM/COMMENT
Open
Will contribute to the premature failure
of the fan relay contacts.
Diode 2
w40 and w41
Fan motor flyback diode
Closed
The 30-amp fuse (on w109) will blow
repeatedly until the diode has been
replaced.
Open
Will contribute to the premature failure
of the key switch contacts.
Diode 3
w123 and w130
Fuel pump and hold coil flyback diode
Closed
The 30-amp fuse (on w125) will blow
repeatedly until the diode has been
replaced.
Open
Will contribute to the premature failure
of the start relay contacts.
Diode 4
w129 and w131
Starter solenoid coil flyback diode
Closed
The 30-amp fuse (on w109) will blow
repeatedly until the diode has been
replaced.
TEST PROCEDURE 13 – Diode 1 on wire 32
See General Warnings, Section 1, Page 1-2.
1.
Disconnect battery.
See Disconnecting the Battery – Gasoline/Diesel Vehicles, Section 1, Page 1-3.
2.
Disconnect the two-pin connector between the front gearcase and the wire harness.
3.
Set the multimeter to the diode test function.
4.
Connect the black (–) probe of the multimeter to the frame (ground).
5.
Connect the red (+) probe of the multimeter to the 18-gauge gray wire (w35) on the two-pin connector (wire
harness side).
See following NOTE.
NOTE:
Ensure probe is connected to the correct gray wire. Gray wire (w33) is powered up by the key switch. Gray
wire (w35) is attached to diode 1.
6.
The reading should indicate an over limit (no continuity). If the diode conducts current (shows continuity) with
the meter probes connected as described, the diode has failed and must be replaced.
7.
Reverse the multimeter probes and note the reading. The multimeter should indicate approximately 540 mV,
however, a range of 400 to 700 mV is acceptable.
8.
If the readings obtained in the previous steps are incorrect, replace the diode.
TEST PROCEDURE 14 – Diode 2 on wire 40
See General Warnings, Section 1, Page 1-2.
1.
Disconnect battery.
See Disconnecting the Battery – Gasoline/Diesel Vehicles, Section 1, Page 1-3.
2.
Raise the hood.
3.
Disconnect the two-pin connector between the fan and the wire harness
4.
Set the multimeter to the diode test function.
2013 Carryall 295/XRT 1550 Maintenance and Service Manual
Page 12-25
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