Volvo TAD650VE, Руководство по ремонту, Страница: 35 / 160

Group 30: Electrical system Malfunctions
33
Manual fault tracing in bus
cables
Special tools:
Multimeter ..................................................... 9812519
IMPORTANT! Cut the current with the main
switch before the cables are disconnected.
Use the multimeter to check the bus cables. The con-
ductors in the bus cables should not be in contact
with each other.
Disconnect a bus cable at each end and measure the
resistance between the pins to check this. The multi-
meter should show infinite resistance between each
pin. If the resistance is less than infinite, there is a
fault.
Measuring the engine cables
Two types of measurement are done on the engine
cable harness, both resistance measurement and volt-
age measurement.
The measurements are done to ensure that no open
circuits or short circuits occur.
If there is an open circuit, the resistance is infinite,
and if there is a short circuit, it is close to zero. The
resistance values given in the workshop manual are
approximate, and should be regarded as guidelines.
NOTE!
When resistance measurement is done, the engine
should be stopped and system voltage should be
cut off with the main switch.
All resistance measurement is done at +20°C
(68°F) and with a cold engine.