Taylor-Dunn B0-T48-48 Taylor Truck T48 Operation Manual page 117

Test 5. CONTACTOR COIL FAULT
Disconnect the 12-pin logic card connector from the Sevcon power unit.
Turn the key switch ON and perform the following tests:
TEST 5.1:
Check the voltage on the positive coil terminal of the
ISO solenoid (violet wire).
If the voltage is within approximately 1-volt of the
battery voltage, then skip ahead to test #5.2.
If the voltage is not within approximately 1-volt
of the battery voltage, then check the diode in
the positive wire to the ISO solenoid.
Stop trouble shooting here and repair the problem.
When the repair is completed, completely retest the
vehicle before lowering the drive wheels to the
ground.
TEST 5.2:
Check the voltage on the negative coil terminal of the
contactor coil.
If the voltage is not within 1-volt of battery voltage,
then the contactor is bad and must be replaced.
NOTE: An open contactor coil should be
accompanied by a 4-flash code from
the logic LED.
If the voltage is within 1-volt, then one of the four
following faults may have occurred:
Broken Wire: Check the wire from pin #8 in
the 12-pin logic card connector to the
contactor coil negative terminal for open
circuits.
Welded Solenoid Contacts: Test the solenoid for welded contact tips. There are two
methods for checking the contacts:
1. Disconnect the batteries and test the continuity across the contacts. If there
is continuity then the contact tips are welded.
2. With the key switch OFF, check the voltage at the B+ terminal on the Sevcon
control (see illustration on following page). If the voltage at the B+ terminal
is at full battery voltage then the contact tips are welded.
NOTE: Welded tips should be accompanied by a 4-flash code from the
logic LED.
Electrical Troubleshooting
Section 4 Page 15