Lull 944E-42 Service Manual - Manual (Page 541)

9.31 Model 644E-42/944E-42 Rev. 6/04
Electrical System
Testing for Continuity
The following procedures verify good continuity in a
circuit.
With a DMM
1. Set the rotary dial of the DMM to the Ohm position.
2. Disconnect the power feed (i.e. fuse, control module)
from the suspect circuit.
3. Disconnect the load.
4. Press the MIN MAX button on the DMM.
5. Connect one lead of the DMM to one end of the
circuit to be tested.
6. Connect the other lead of the DMM to the other end
of the circuit.
7. If the DMM displays low or no resistance and a tone
is heard, the circuit has good continuity.
With a Test Lamp
IMPORTANT: Only use the test lamp procedure on low
impedance power and ground circuits.
1. Remove the power feed (i.e. fuse, control module)
from the suspect circuit.
2. Disconnect the load.
3. Connect one lead of the test lamp to one end of the
circuit to be tested.
4. Connect the other lead of the test lamp to battery
positive voltage.
5. Connect the other end of the circuit to ground.
6. If the test lamp illuminates (full intensity), then the
circuit has good continuity.
Testing for Short to Ground
The following procedures test for a short to ground in a
circuit.
With a DMM
1. Remove the power feed (i.e. fuse, control module)
from the suspect circuit.
2. Disconnect the load.
3. Set the rotary dial of the DMM to the Ohm position.
4. Connect one lead of the DMM to one end of the
circuit to be tested.
5. Connect the other lead of the DMM to a good
ground.
6. If the DMM does NOT display infinite resistance
(OL), there is a short to ground in the circuit.
With a Test Lamp
1. Remove the power feed (i.e. fuse, control module)
from the suspect circuit.
2. Disconnect the load.
3. Connect one lead of the test lamp to one end of the
circuit to be tested.
4. Connect the other lead of the test lamp to battery
positive voltage.
5. Connect the other end of the circuit to ground.
6. If the lamp illuminates (full intensity), then the circuit
has good continuity.
Testing a Fuse Powering Several Loads
1. Review the system schematic and locate the fuse
that is open.
2. Open the first connector or switch leading from the
fuse to each load.
3. Connect a DMM across the fuse terminals (be sure
that the fuse is powered).
• When the DMM displays voltage the short is in
the wiring leading to the first connector or switch.
• If the DMM does not display voltage, refer to next
step.
4. Close each connector or switch until the DMM or
analog tester displays voltage in order to find which
circuit is shorted.