If the excavator A/C system shows no blower motor function, no A/C switch light and no A/C compressor function, do the following check:
Remove the two bolts and fuse / relay cover (Item 1) [Figure 70-30-4].
Check the HVAC fuse (Item 1) and controller fuse (Item 2) [Figure 70-30-5].
Replace the fuse if burned out. If the fuses are good, remove the relay (Item 3) [Figure 70-30-5].
Using a multimeter, check the voltage at the following relay terminals:
Voltage at pin 30 (Item 1) [Figure 70-30-6] is 12 volts at all times.
Voltage at pin 86 (Item 2) [Figure 70-30-6] is 12 volts when the start key is in the on position.
Pin 85 (Item 3) [Figure 70-30-6] is ground. Check for continuity to the ground.
With the key in the ON position, A/C switch ON, turn the fan switch ON pin 87 (Item 4) [Figure 70-30-6] is ground.
Turn the fan switch OFF, and there is no continuity.
If the voltages and continuity checks are OK but the problem still persists, replace the A/C relay (Item 1) [Figure 70-30-7].
Check to see if the compressor clutch is engaging.
With a person in the operator seat and the cab door open, turn the key switch to RUN (Standard panel) OR press the RUN / ENTER Button (Deluxe Panel), without starting the excavator.
Push the A/C switch (Item 1) to the ON position. Turn the blower fan switch (Item 2) [Figure 70-30-8] to the first ON position.
The compressor clutch should make a click sound, which indicates the clutch is engaging.
NOTE: There is a time delay of 5 – 10 seconds until the clutch will engage.
Disconnect the wire harness (Item 1) [Figure 70-30-9].
NOTE: The counterweight is removed for photo clarity.
With a multimeter, check the resistance to the compressor clutch.
If there is no resistance value, replace the compressor. (See Removal And Installation on Page 70-50-1.)
With a multimeter, check the voltage to the compressor clutch at the wire harness.
If the voltage reading is approximately 12 volts, the system is operating correctly.
If there is no power at the clutch, reconnect the wiring harness to the compressor clutch.
