Taylor-Dunn B0-248-TT, Operation, T Roubleshooting And Replacement Parts Manual, Page: 121 / 204

Maintenance, Service, and Repair
Electrical Troubleshooting
Page 11
Contactors
Troubleshooting in the procedure assumes that the control
system is functioning (output from M- on controller) and
that the motor has tested good.
Both the forward and the reverse contactors pass current
in both directions. This means that a failure in either
contactor could result in not running in the opposite
direction.
If the vehicle runs in either forward or reverse, then the ISO contactor is good.
! Perform tests at Contactor Negative Return before completing this procedure. !
ISO Contactor
Close seat interlock switch and turn the key switch ON.
> The ISO contactor should close.
> If the contactor did not close, check if there is Control Volts across the contactor
coil.
If the voltage is good, replace the contactor.
If the voltage is bad, check the seat interlock switch, key switch, and wiring.
> After the contactor closes, test the voltage on both the hot and cold terminals on
the contactor. The voltage should be battery volts on both terminals.
If the hot terminal is bad, check circuit breaker and wiring to battery.
If the hot terminal is good but the cold terminal is bad, then replace the contactor.
If both terminals are good, the contactor is functioning properly.
Forward/Reverse Contactor:
These contactors have two sets of contacts, Normally Open (NO) and Normally Closed (NC). When
a direction is selected and one of the contactors picks up, current will pass through the NO contacts
on the energized contactor and the NC contacts on the other contactor. The easiest method of
checking the contacts is with a test light, this way the wires do not have to be removed from the
contactors.
Connect the test light across the NC terminals of the REVERSE contactor.
Close seat interlock switch and turn the key switch ON, select the FORWARD direction and depress the
throttle pedal.
> The light should be OFF.
If the light is ON, then replace the contactor.
Connect the test light across the NO terminals of the FORWARD contactor and depress the throttle pedal.
> The light should be OFF.
If the light is ON, then replace the contactor.
Connect the test light across the NC terminals of the FORWARD contactor.
Close seat interlock switch and turn the key switch ON, select the REVERSE direction and depress the
throttle pedal.
> The light should be OFF.
If the light is ON, then replace the contactor.
Connect the test light across the NC terminals of the REVERSE contactor and depress the throttle pedal.
> The light should be OFF.
If the light is ON, then replace the contactor.
If the light did not come on during any test, it is likely that the fault is not in the forward
or reverse contactor.
These test procedures must be
performed in the order they were
written. If the test result is good,
then proceed to the next test or go
to the next section. Failure to do so
may result in incorrect test results.