Taylor-Dunn TT-316-36 Operation, T Roubleshooting And Replacement Parts Manual Download

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Sevcon Troubleshooting

Page 5

Electrical Troubleshooting

Test 1. CHECKING THE CONTROL LOGIC
INPUTS

Close the seat switch. Place the high/low switch in
the HIGH position.

Connect a voltmeter across the ISO solenoid coil
terminals and carefully monitor the voltage as the
key switch is turned on.

Turn the key switch ON and wait 1-second until
the Isolator contactor closes.

Perform the following tests:

TEST 1.1

The coil voltage should start at approximately 24
volts when the key is turned ON, then drop to
approximately 15 volts after about 0.5 seconds.

If the test is good, then skip ahead to test #
1.2.
If the voltage starts high, drops to 15 volts,
and then drops to 0 volts, then it indicates
an open circuit to the main battery positive.
Check the continuity of the ISO solenoid
contacts, the main circuit breaker, and the
wiring to the main battery positive post.
If the voltage is starts at 24 volts but the
solenoid does not pick up, then skip ahead
toTest #5.
If the voltage does not start at 24 volts, then
go to Test #4.

TEST 1.2:

Test the voltage from B+ to B- on the Controller.

If the voltage equals battery volts, then go
to Test #1.3.
If the voltage does not equal battery volts,
then:

•

Check the main positive wire to the circuit
breaker for open circuits.

•

Check the wire from the circuit breaker to
battery positive.

•

Check the wire from the contactor to B+ on
the controller for open circuits.

•

Check the wire from B- to battery negative
on the controller for open circuits.

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 1.3:

Test the voltage at pin #6 on the 12-pin logic card
connector.

If the voltage is low, then skip ahead to Test
#1.4.
If the voltage is high, then check the wire to
the High/Low switch and the High/Low
switch for open circuits.

NOTE: The High/Low switch is optional and the

vehicle may not have this option. If the
vehicle is not equipped with option then there
is a jumper bypass installed in place of the
switch in the dash. Check the jumper to be
sure it is still connected.

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.

STOP

TEST 1.4:

Test the voltage at pin #5 on the 12-pin logic card
connector.

If the voltage is low, then skip ahead to Test
#1.5.
If the voltage is high, then:

•

Check the seat switch for open contacts.

•

Check that the seat switch is engaging the
seat correctly.

•

Check the wire from the pin 5 to the seat
switch for open circuits.

•

Check the wire from the seat switch to B-
for open circuits.

If all of the above is in working order, then the
logic card may have failed.

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.

Stop, do not continue. Reaching this point
indicates a failure in the Sevcon power unit
or an error was made during testing. Confirm
all previous tests were performed correctly
before replacing the Sevcon power unit.

STOP