FORM NO. 56043071 CMAX
™
28/34ST / I-MAX
™
28/32C, BA 750/850ST, BA 750C -
45
WHEEL DRIVE SYSTEM
No Fwd or Rev wheel
drive (see Figure 1).
At the A2 speed controller
check for 24/36V input, Brn
wire to Negative battery
standoff
Repair or replace the
Brn control circuit
input wire.
Check the total resistance of the
drive paddle R1 pot. Remove wires
and measure across the two out-
side terminals, should read 4500-
5500 Ohms.
Test shows an open
(infinity) replace the R1
potentiometer with P.N.
56397029
Check the total resistance of
the speed limit R2 pot. Remove
wires and measure across the
two outside terminals, should
read approximately 25000
Ohms.
Separate the motor wiring harness
disconnect (see Note B) & check
for controller output voltage by acti-
vating the drive paddle.
•24V machines should have 24V in
Fwd & 18V in Rev.
•36V machines should have 36V in
Fwd & 28V in Rev.
Test shows an open
(infinity) replace the R2
potentiometer with P.N.
56397123
Replace the A2
speed controller
Check the functional operation of
the wiper resistance circuits (see
Note A) for both the 5K(R1) pot &
the 25K(R2) pot.
Test measurements should show a
variable resistance within spec. for
each individual pot when the pot
shaft is turned in both directions.
Replace the specified
pot(s) that's measure-
ments show an open
circuit.
Yes
Yes
Yes
Yes
No
No
No
No
No
SYMPTOM ONE
Note: Do all testing with control panel R2 speed limiting pot in the maximum position, the drive wheel jacked up off the floor, key switch ON, and
the drive paddle activated (pushed Fwd or pulled into Rev.)
Part B: Wheel drive system motor control circuit troubleshooting guide
Note A:
Follow the potentiometer test instructions shown in the Wheel Drive System.
Note B:
The drive wheel motor harness disconnect is located in the lower rear of the machine frame next to the right rear caster wheel.
TROUBLESHOOTING GUIDE ELECTRICAL (CONTINUED)