JLG 3246ES Service Manual - Manual (Page 189)

SECTION 7 - GENERAL ELECTRICAL INFORMATION & SCHEMATICS
3121166 – JLG Lift – 7-13
Switch Wiring - Low Side, High Side
When controlling a load, a switch can be wired between the positive side of the power source and the load. This
switch is called a "high side" switch. The switch supplies the power to the load. When a switch is wired between the
negative side of the power source and the load, it is a "low side" switch. The switch provides the ground to the load.
A low side switch will allow voltage to be present on the load. No power is applied because the switch is stopping
current flow. This voltage can be seen if the measurement is taken with one test lead on the load and the other on the
battery negative side or grounded to the vehicle. What is actually being measured is the voltage drop across the
switch. This could mislead a technician into thinking the load is receiving power but not operating. To produce an
accurate picture of power or voltage applied to the load, measure voltage across the load’s power terminals. Also, the
technician can measure the voltage at both power terminals with respect to battery ground. The difference between
those two measurements is the voltage applied to the load.
7.6 CIRCUIT BOARDS: INPUTS AND OUTPUTS
Table 7-1. Ground Board J1 (1600346 Power Module ONLY)
Pin Function Type Range (V)
1 Ground Power Output 0
2 Analyzer Power Power Output 12
3 RS-232 Receive Input/Output Comm
4 RS-232 Transmit Input/Output Comm
5 Platform EMS Input Vbatt
6 Ground Power Output 0
7 Ignition Power Output Vbatt
8 Platform EMS Source Power Output Vbatt
9 Ignition Power Output Vbatt
10 Left PHP Switch Input Vbatt
11 CAN Bus high Input/Output Comm
12 CAN Bus Low Input/Output Comm
13 CAN Bus Shield Power Output 0
14 Analog Power Power Output 5
15 Elevation Angle Sensor Input 5
16 Ground Power Output 0
17 Ignition Power Output Vbatt
18 Right PHP Switch Input Vbatt
19 Ignition Power Output Vbatt
20 Brake Release Swtich Input Vbatt
21 Steer Left Coil Output Vbatt
22 Steer Right Coil Output Vbatt
23 Left Brake Release Output Vbatt
24 Right Brake Release Output Vbatt
25 Lift Up Coil Output Vbatt
26 Lift Down Coil Output PWM
27 Ground Power Output 0
28 Ground Alarm Output PWM
29 Charger Interlock Input Vbatt
30 Ground Power Output 0
31 CAN Bus High Input/Output Comm