Testing Relays - Komatsu PC200-8M0 Shop Manual

100 Air conditioner

Testing relays

Testing relays
a If the air conditioner compressor is normal (air is
cooled), omit this test since the relays are nor-
mal.
q Compressor clutch relay R21:
Turns the air conditioner compressor (clutch)
ON/OFF.
a See Step 2 on "Parts and connectors layout".
Testing
1. Check contact R21 of connector (for disconnec-
tion).
2. Turn the starting switch ON (do not start the
engine), turn the main power of the air condi-
tioner ON, and turn the air conditioner switch. If
the compressor relay is normal, it is turned ON.
Check whether its clicks.
a The air conditioner controller will not turn on
the compressor clutch relay in the following
cases.
1) When the evaporator temperature is below
3 °C (depending on the input voltage from
the evaporator temperature sensor).
2) When the dual pressure switch detects
abnormality (it is turned OFF).
PC200, 200LC, 220, 220LC-8M0
Checking relay unit
q
a Since no T-adapter is available, it is impossible
to check the relay while the voltage is applied to
the coil actually.
Compressor clutch relay (RLCC), connector (R21)
1) The coil resistance between terminals (1)
and (2) is approximately 300 to 500 z.
2) While voltage (DC 20 to 30 V) is not applied
between terminals (1) (+) and (2), terminals
(3) and (4) are connected.
3) While voltage (DC 20 to 30 V) is applied
between terminals (1) (+) and (2), terminals
(3) and (5) are connected.
SEN06151-00
37
80-100