Taylor-Dunn C0-425-36 Operation, Troubleshooting And Replacement Parts Manualooting And Replacement Parts Manual page 164

Electrical Troubleshooting
Test 3. THE VEHICLE RUNS IN ONE DIRECTION ONLY
Test 3.1:
Close the seat switch, turn the key switch ON and wait
1-second until the Isolator contactor closes.
If the vehicle runs in reverse only then skip ahead to
test #3.3.
Place the forward and reverse switch in the FORWARD
direction.
Test the voltage at pin #2 on the 12 pin logic card
connector.
If the voltage is low, then skip ahead to test #3.2.
If the voltage is high, then skip ahead to Test #7.
TEST 3.2:
Test the voltage at pin #3 on the 12 pin logic card
connector.
If the voltage is high, then skip ahead to test #3.3.
If the voltage is low, then skip ahead to Test #7.
This troubleshooting guide is written in sequential order. All tests
must be performed in the order that they are written. Starting in the
middle or skipping sections when not instructed to do so may lead to
invalid test results.
Troubleshooting Page 10