Table 3-1. Protective Circuit Voltage Tests

caution: For measurements with the

should read 2 to 2.5 volts, indicating the protective circuit

is not tripped. If the full battery voltage is read, the circuit

accelerator pedal down, proceed as

is tripped and must be reset before continuing.

rapidly as p1ossibltl to avoid burning out

(4) Make the voltage measurements of table 3-1

the 10 ohm resistor in the contactor unit.

Table 3-1. Protective Circuit Voltage Tests

Voltmeter lead

Select

Accelerator

Voltage

connection

direction

pedal

reading

Positive

Negative

(Red)

(Black)

Yes

Down

B+

Full battery voltage

B+

Full battery voltage

B+

Less than 5 volts

B+

3 volts

B+

5 volts

B+

Full battery voltage

* Do not hold accelerator pedal In the down position These test should be accomplished as rapidly as possible

b. Trouble Analysis. If all of the voltages are

3-12. Directional Control Switch

correct, likely causes of trouble are as follows.

a. General. The directional control switch is a lever-

(1) Protective circuit trips when direction is

operated, double-pole, double-throw switch with a center

selected due to:

off position. Detents are provided to hold the switch in

(a) Defective control unit-low bias.

any of its three positions.

(b) Defective power switch-open emitter,

b. Removal. Remove the directional control switch

shorted base to collector.

according to paragraph 2-8.

Disassembly. (fig. 3-20.)

(2) Protective circuit trips when pedal is

(1) Squeeze contact finger assemblies (6)

depressed only far enough to operate microswitch due

together, rotate 1/2 turn, and withdraw assemblies and

to:

contact finger spring (7).

(a) Open or intermittent 10 ohm resistor in

(2) Remove screws through terminal board

contactor unit.

assemblies (8 and 9) and remove assemblies.

(b) Shorted power switch.

(3) Unhook handle springs (10) from pins and

(3) Protective circuit trips when

pedal is

remove.

depressed far enough to generate a drive signal due to:

(4) Remove screws holding clips (11 ) and

(a) Defective control unit-low drive.

remove clips and arms.

(b) Open, intermittent, or wrong value in

(5) Remove screw and washers holding carrier

assembly and remove assembly.

resistor assembly.

c. Removal. Tag and disconnect the leads and

(6) Remove operating shaft assembly (15),

washer (16), and spacer (17).

remove according to figure 3-13.

d. Cleaning.

d. Installation. Install the protective circuit according

(1) Blow dust from parts with compressed air

to the reverse of removal.

under moderate pressure.

3-32