Taylor-Dunn B0-248-TT, Operation, T Roubleshooting And Replacement Parts Manual, Page: 116 / 204

Maintenance, Service, and Repair
Electrical Troubleshooting
Page 6
Controller Small Signal Input
During this procedure, voltages will be measured at the controller terminals #1, #2, #6, and #7.
Close the seat interlock switch, turn the key switch ON, select a direction and fully depress the throttle
pedal.
> Terminal #1 should be 12 Volts (nominal).
> Terminal #2 volts should vary between 6 and 11 Volts (nominal) depending on throttle
pedal position.
> In Forward, terminal #6 should be 12 Volts (nominal).
> In Reverse, terminal #7 should be 12 Volts (nominal).
If Terminal #1 failed: Go to Forward/Reverse Switch section for your vehicle.
If Terminal #2 failed: Go to Throttle Module.
If Terminal #6 or #7 failed: Go to Forward/Reverse Switch section for your vehicle.
Forward/Reverse Switch, Model ET-150-74 (72 volt system)
The Forward/Reverse switch assembly consists of two micro switches and three diodes. Diodes D2
and D3 provide power to the #1 terminal on the controller. Diode D4 is a blocking diode to isolate the
reverse light circuit from the control system.
During this procedure, voltages will be measured at F/R switch Green/Black wire, White/Black wire,
cathode of D4, NO terminal of reverse switch.
Turn the key switch ON, select FORWARD direction and depress the throttle pedal.
> Green/Black wire should be Control Volts.
> White/Black wire should be Control Volts.
> All others should be LOW.
If Green/Black wire is LOW, go to Throttle Module.
If White/Black wire is LOW, replace the forward switch.
If any other wire or tested terminal is Control Volts, then check the reverse switch and
wiring for shorts.
Turn start switch ON, select REVERSE direction and depress the throttle pedal.
> NO terminal on reverse switch should be Control Volts.
> D4 Cathode should be Control Volts.
> All others should be LOW.
If NO terminal is LOW, replace the reverse switch.
If D4 cathode is LOW, replace the diode.
If any other wire or tested terminal is High, then check the forward switch and wiring for
shorts.
If all above tests are good, then check wiring from F&R switch to the control panel
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.