Siemens 16#000A: Siemens S7-1500 Error Code 16#000A

Symptoms

The SF LED turns red. The CPU detects that the supply voltage has dropped below the minimum rated voltage for proper operation. The CPU enters STOP mode to prevent data corruption.

Possible Causes

Power supply unit failure or degradation
Excessive load on the 24V DC power supply
Loose or corroded power supply connections
Voltage drop due to long cable runs or undersized wiring

Troubleshooting Steps

Step 1: Measure the DC voltage at the CPU power supply terminals
Voltage reading should be between 21.6V and 26.4V DC
Step 2: Check the total current draw on the 24V DC power supply
Total load is within the power supply rated capacity
Step 3: Inspect all power supply wiring for loose connections or corrosion
All connections are tight, clean, and making good contact
Step 4: If the power supply is undersized, upgrade to a higher-capacity unit
Voltage remains stable under full load conditions

How to Reset

To reset: 1) Restore stable 24V DC power to the CPU. 2) If the CPU is in STOP mode, switch it to RUN mode. 3) Clear the diagnostic buffer. Caution: Low voltage can cause data corruption, so verify all program data and configuration before restarting.

Common Replacement Parts

6EP1334-2BA20: SITOP power supply 24V/8A (Ensure adequate current capacity for all connected loads)

Frequently Asked Questions

Q: What causes low voltage on a 24V DC system?
Common causes include undersized power supplies, excessive load, long cable runs with voltage drop, or corroded connections adding resistance.
Q: How do I size a power supply for my PLC system?
Calculate the total current draw of all modules and devices, then add a 20-30% margin. Account for inrush currents and peak loads during operation.

Siemens S7-1500 Error Code 16#000A