FANUC I/O Unit A Maintenance Manual

If the main station displays that all groups are not connected, it may be due to a fault in the main station itself or an open circuit in the first section of the cable.

8.2 Output module has no output

Check if the corresponding Y address in the PMC program is set to 1.

Observe module LED: If the LED is on but the external load does not operate, measure the output voltage/current. For source type output (POS), connect one end of the load to the output point and the other end to 0V; for drain type (NEG), connect the load to+24V. Check if the common terminal (CM) wiring is correct.

For modules with fuses, check if the F light is on. If it lights up, replace the fuse (must be of the same specification: 5A or 3.15A) and check if there is a short circuit in the load.

For modules with protection function, if the F light is on and the output is turned off, it will automatically recover after the module cools down. If triggered repeatedly, check whether the load is overcurrent (such as low resistance of the solenoid valve coil).

8.3 Abnormal analog readings

For current input, check if I+and V+have been short circuited and if the 250 Ω input resistor (built-in to the module) is correctly connected.

Check common mode voltage: The COM terminal must be connected to the signal reference ground.

Use a standard signal source to test the corresponding range value of the module (e.g. 4-20mA should display 0~4095 or 0~20000 depending on the module). If the deviation is too large, it may be due to module damage or improper filter settings.

8.4 High speed counter does not count

Check the encoder power supply (+5V provided by module JA9, maximum 300mA) and cable connections.

Confirm pulse type selection: PSEL pin open circuit=phase A/B; Grounding=positive/negative pulse.

Confirm that the CE (count enable) control bit is 1 and the external CSP input is not closed.

Observe whether the panel A/B LED flashes with the pulse (it may remain on at high frequencies).

If the ALM light is on, it indicates a wire break or short circuit. Check the differential signal line and terminal resistance.

8.5 Temperature module reading shows "-" or abnormally high

Check the wiring of the sensor: Three wire system for thermal resistance (short circuit required for two-wire system), and ATB01B terminal unit for thermocouple.

Check the DI13/DI29 (exception flag) of the PMC input status word. If set to 1, read the exception codes from DI00 to DI12: for example, DI01=1 indicates CH1 disconnection, DI04=1 indicates cold junction abnormality (thermocouple).

Confirm that the module type and sensor type settings (DO17, DO18) are consistent with the actual settings.

Key points of safety and certification

UL/CSA certification: The UL certification unit order number starts with A03B-0819-Jxxx or A03B-0826-Jxxx, and the flame retardant rating of the shell is 94V-0. During installation, it is necessary to meet pollution level 2, overvoltage category II, use AWG16 or above wires, and isolate the 24V power supply.

CE Mark: Compliant with the EMC Directive (2014/30/EU) and the Low Voltage Directive (2014/35/EU), in accordance with EN 61131-2.

Korean KC mark: Industrial Class A equipment, not suitable for home environments.

Installation environment: temperature 0~55 ℃, relative humidity ≤ 75%, no condensation, altitude ≤ 1000m (decrease by 1 ℃ every 100m at higher altitudes). Avoid direct contact with cutting fluid and oil mist.