Under voltage Test.

according to movement of accelerator pedal. If not,

(5) Set voltmeter to 50 volt scale. Connect

speed potentiometer is defective.

between control unit terminal 2 (+ lead) and

(10) Remove the cardboard insulation from the

terminal 3 (- lead)

contractors.

(6) Short circuit brake interlock switch by

b. Under voltage Test.

connecting insulated wire with alligator clips between its

two terminals.

(1) Disconnect

battery

and

discharge

(7) Connect battery and turn key switch on.

capacitors (para 2-5).

Caution: Do not allow peak-reading

(2) Insulate the tips of all contractors on

contactor unit with thin cardboard (except EC contactor).

meter indication to exceed 800

(3) Disconnect the two wires from terminal 8 on

ampers at any time.

the control unit. Connect the two wires together.

(8) Set directional control switch to forward (F)

(Two n ale spade terminals connected by a one inch

position. Stall drive wheels using service brake.

piece of wire make a useful tool for this purpose.)

(9) Observe both meters and slowly depress the

(4) Connect a wire from the negative battery

accelerator pedal.

The voltmeter reading should

terminal to terminal 8 on the control unit.

increase to the full battery voltage at the current limit

(5) Connect the battery and turn the key switch

point. This should occur between 720 and 760 amperes.

on.

(10) If current limit point is incorrect, control unit

(6) Connect the voltmeter between control unit

requires repair.

terminal 2 (+ lead) and terminal 3 (- lead). The voltmeter

(11) Disconnect battery and

discharge

should read the full battery voltage.

capacitors (para 2-5).

(7) Move the wire from the negative battery

(12) Disconnect voltmeter, peak-reading meter,

terminal to each other battery terminal, working toward

and shunt.

the positive terminal. When the voltmeter, reading

(13) Reconnect truck lead to terminal B2-.

drops to about one-half volt, measure the voltage

(14) Remove the short circuit from the brake

between the positive terminal and the terminal that

interlock switch.

produces the under voltage condition. This voltage must

d. Inching Control Adjustment. The inching control

be between 20 and 24 volts. If not, the control unit

adjustment is made following the speed potentiometer

requires repair.

adjustment of paragraph 3-6f.

(8) Disconnect battery and discharge capacitors

(1) Raise and block the drive wheels. Warning:

(para 2-5).

Be sure drive wheels are clear of blocks and ground.

(9) Disconnect the jumper wire to battery and

(2) Set the directional control switch to the

the juniper between the two wires. Reconnect the two

forward (F) position.

wires to control unit terminal 8. Remove the insulation

(3) Depress the accelerator pedal 1/2 inch

from the contactor unit.

beyond the point where the microswitch in the peed

c Current Limit Test.

control box assembly operates.

(1) Disconnect

battery

and

discharge

(4) Adjust inching control R36 on the control unit

capacitors (para 2-5).

to the point where the drive wheels just barely begin to

(2) Disconnect truck lead from B2- terminal.

rotate. (fig. 3-12.)

Connect 50 millivolt, 500 ampere shunt between truck

e. Removal

lead and B2- terminal.

(1) Disconnect

battery

and

discharge

(3) Connect peak-reading meter in parallel

capacitors (para 2-5t.

across shunt: Red lead to shunt terminal at B2--;black

(2) 'Tag and disconnect the leads.

lead to other shunt terminal.

(3) Remove the five nuts (1. fig. 3-13) and

(4) Set peak-reading meter to 1000 ampere

remove the control unit.

scale.

3-23