1. A fan irregularity signal, excessive current draw due to binding. Examine M4 for obstructions which may bind the fan. Check the M4 fan lock signal (main CB, CN26-4) in the 47 mode, input code 42. The voltage should be between 0.1 to 0.2V DC. If 5V DC is present, either the fan is binding or the fan is defective. Replace M4 (p/n 25HA80512).
Note: If the fan lock signal is normal, install the version 17.0 EPROM (p/n 101517-17.0) to prevent false F54 errors as outlined in 1015/1212 Technical Bulletin #15
2. IC7 on the main CB has shorted due to a failed total counter. IC7 shares the 24V DC control signal line with the exposure lamp, separation solenoid (SD1), registration solenoid (SD2), total counter, key counter, and cooling fan (M4). All loads except the total counter operate in diagnostics.
Replace the total counter (p/n 466088201) and the main CB (p/n 25HE-7312).
3. A poor connection between the cooling fan (M4) and the main CB. Reseat CN73 at M4 (cooling fan) and CN26 on the main CB.