Bosch ACS 653 Repair Instruction page 101

Plumbing and Mechanical
ACS 653, ACS 663 Service Manual
REFRIGERANT IDENTIFICATION PROCESS (for ACS 663-RI only)
When the recover or tank fill function is selected, the machine will check pressures on the service hoses.
Once pressure is verified the machine will initiate identification of the refrigerant. The low side identifier solenoid
(S17) will open intermittently, allowing refrigerant to flow to the refrigerant identifier, through the 0.028-inch internal
diameter orifice. After analyzing the refrigerant, the identifier will either send a "PASS" message to the control board
to begin the recovery process, or a "FAIL" message will display. If the refrigerant fails to pass the ID test, the machine
will print the results, and ask if you want to repeat the ID test. If the refrigerant ID test, fails, the test will automatically
repeat at least two more times.
Figure 4-9. Refrigerant Identification
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Robert Bosch GmbH SP00D00624 2021-04-08