Testing (Dual) Pressure Switch For Refrigerant - Komatsu PC88MR-10 Shop Manual

Testing (dual) pressure switch for refrigerant

Place the machine on a level ground, lower the work equipment to the ground and stop the engine.
Turn the battery disconnect switch to the OFF position and remove the key.
a Note the connector numbers and installed positions before disconnecting wiring harnesses and hoses.
Testing
(PC88MR-K5FG-360-K-00-A)
If [879GKX] "Refrigerant Press Input Sig Out of Range" is displayed by the self-diagnosis (on "03 Air-
conditioning System" screen of "Abnormality Record" in the machine monitor), test the dual pressure
switch connector P17.
To reset the self-diagnosis system (detection of abnormality), the starting switch must be turned OFF.
The dual pressure switch is ON when the refrigerant pressure is normal, and OFF when it is abnormal.
a If ambient temperature drops to 0 °C or below, refrigerant pressure will also subsequently decrease.
Accordingly, there is a possibility that the dual pressure switch is OFF. In such a case, the dual pressure
switch unit is not defective but normal.
1. Referring to "Parts and connectors layout" "6. Dual pressure switch", remove the tool box.
2. Disconnect the dual pressure switch connector P17.
3. Check if the resistance between the switch-side terminals of connector P17 are shorted (ON). (If not
shorted (OFF), dual pressure switch is detecting an abnormal refrigerant pressure.)
a If the dual pressure switch is OFF, attach a pressure gauge to the high-pressure line of the air
conditioner compressor and check the refrigerant pressure. See "Connection of service tool" and
"Troubleshooting with gauge pressure".
a If the refrigerant pressure is normal, the dual pressure switch is defective.
(Dual) pressure switch
LA: 0.20 MPa {2 kg/cm 2
LB: 0.02 MPa {0.2 kg/cm
HA: 3.14 MPa {32 kg/cm
HB: 0.59 MPa {6 kg/cm 2
PC88MR-10
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Testing (dual) pressure switch for refrigerant

(PC220-K5FG-001-K-00-A)
80 Appendix
80-45