Specifications
62
Capacitor 1C
Disconnect the battery and discharge the capacitor. Measure ohms through the capacitor using the R x
10,000 scale. Meter should read zero and then swing slowly to above 100,000 ohms. Replace the
capacitor if above reading is not obtained.
Contactors F, R, 1A,SP,FW,D,REGEN and P
150 ampere contactors instruction sheets.
300 ampere contactors instruction sheets.
NOTE:
Control is arranged so that the F and R contactors do not break current. Check to see that the
1A contactor drops out before the F or R contactor.
Most contactor coils are polarity sensitive. The left-hand terminal must be connected to
positive.
Potentiometer in Accelerator
To check operation of the potentiometer, disconnect the battery and disconnect the wire at
control card TB1. Connect a VOM to the wire that was removed from TB1 and to nega-
tive. Place the VOM on the R x 100 scale. With the accelerator in the creep speed position,
the ohms reading should be 4800 to 6000 ohms. With the accelerator in the top speed
position, the ohm reading should be 50 ohms or less. With the wire disconnected as above,
check for resistance of 1 megohm or higher from pot wire to the truck frame.
SCRs (1REC, 2REC,5REC)
These are silicon controlled rectifiers. Before checking, disconnect the battery and dis-
charge capacitor 1C. Disconnect gate leads of SCRs at the SCR terminal.
To check an SCR, it is necessary to have a 6 volt battery and 2 A-14 diodes.
Connect the positive lead to the anode, connect the negative lead to the cathode as shown
below.