ELECTRICAL SYSTEM AND TESTING: ELECTRIC
VEHICLES
Test Procedures
22
4.
If the reading is zero volts, check the continuity of the green/white wire. if the continuity is good, replace the
speed controller.
TEST PROCEDURE 21 – Onboard Computer Silicon-Controlled Rectifier (SCR) Circuit
See General Warning on page 1-1.
The silicon controlled rectifier (SCR), located inside the onboard computer, acts as a switch on the negative side
of the circuit.
This allows the onboard computer (OBC) to control the battery charging current.
Use the following procedure to test the SCR:
1.
With batteries connected and a multimeter set to 200 volts DC, place the red (+) probe on the positive post of
battery no. 1 and place the black (–) probe on the charger receptacle fuse terminal that has the black 10-gauge
OBC wire (1) attached to it. The reading should be approximately 36-42 volts.
2.
If the reading is zero volts, check the black 10-gauge wire connections at the controller and receptacle. Check the
continuity of the black 10-gauge wires. If the wires and connections are okay, the SCR has failed. Replace the
OBC. If the reading is correct, proceed to the following step.
3.
Plug in AC and DC cords. When the battery charger relay clicks on, reading should be approximately 48 volts
(full battery voltage). If the reading does not rise from approximately 40 volts to full battery voltage when the
DC cord is plugged in and the relay clicks on, check the following items:
– Charger receptacle fuse and black wire terminal socket in the charger receptacle.
– Onboard computer gray wire and fuse.
See Onboard Computer Gray Wire and Fuse on page 22-29.
– Red wire at the charger receptacle.
See Voltage at Charger Receptacle Red Wire Socket on page 22-30.
TEST PROCEDURE 22 – Onboard Computer Gray Wire and Fuse
See General Warning on page 1-1.
1.
With batteries connected and a multimeter set to 200 volts DC, connect the red (+) probe to the positive post of
battery no. 1 and black (–) probe (with insulation-piercing probe) to gray 16-gauge wire (2) at a point between
fuse and receptacle (1). Reading should be approximately 40-45 volts. If reading is zero volts, check gray
wire fuse and fuse holder for continuity.
2.
If the reading in step 1 is 48 volts, plug the DC cord into the vehicle’s charger receptacle. The voltage reading
should drop to approximately less than 5 volts before the charger relay clicks on.
3.
When the charger relay is activated, the reading should rise to approximately 48 volts.
4.
If voltage does not drop to less than 5 volts when the DC cord is plugged in and then rise to approximately 48
volts when the charger relay clicks on, the gray wire circuit in the OBC has failed. Replace the OBC.
2007-2009 Turf 252, Carryall 252 and XRT 900 Maintenance and Service Manual
Page 22-29
