Section 50 - Climate Control - Chapter 1
50-1-76
Low Pressure Switch and Circuit Test
Steps and Test Point Corrective Actions
1. Refer to A/C Troubleshooting Foldout and follow
the conditions for performance testing. Install A/C
high and low side pressure gauges. Low reading
below 4 psi ± 2 psi (28 kPa ± 14 kPa)?
YES - Perform corrective actions from A/C
Troubleshooting Foldout.
NO - Go to next Step.
2. Shut off the tractor. Disconnect the switch from the
harness and the unit. Check that switch is open
across pins A and B.
OK - Go to next Step.
NOT OK - Replace switch.
3. Reinstall the switch in the unit; do not reconnect
the harness. Keyswitch and A/C ON, blower
control on any speed, and temperature control on
maximum cool setting, Is 5V present at pin B at
the harness to the switch?
YES - Go to next Step.
NO - Go to Step 5.
4. Keyswitch OFF. Measure resistance from pin A at
the switch to the HVAC ground stud. Less than 1
ohm?
YES - Go to next Step.
NO - Locate open condition and repair between pin A
and HVAC ground stud.
5. Keyswitch ON. Is 5V present at pin B at the
controller (CCU2)?
YES - Locate open condition and repair between pin B
at the controller and pin B at the switch.
NO - Test the controller. See Standard Controller
Test 65 in this Section.
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