Delta AS Series — ERROR LED Diagnosis in ISPSoft

Delta · beginner · 20 min

A Delta AS/DVP PLC ERROR LED has a specific cause you can read online in ISPSoft. Check PLC Information for the message, fix the cause, and clear latch errors with a STOP/RUN toggle or a power cycle.

ℹ️ Don't guess at a Delta ERROR LED — connect ISPSoft online and read PLC Information. The message tells you whether it's a program, memory, password, or latched-register problem.

Read the error in ISPSoft

On a Delta AS / DVP series PLC, the ERROR LED lights when the CPU detects a fault. To identify it:

1. Open ISPSoft (Delta's current environment for DVP, AS, and AH series; WPLSoft also works for older DVP).
2. Connect in Online Mode to the PLC.
3. Go to PLC → Information (Device Information) and read the specific error message shown there. That message is the fastest route to the cause.

Common error causes

For the AS series, typical error conditions include:

• Damaged program in the PLC.
• Denied access to CPU memory.
• Incorrect PLC ID or incorrect PLC password (and maximum password attempts exceeded).
• Abnormal latched special data registers.

And the most frequent real-world root causes behind faults are loose wires, a bad power supply, or a math error in the code (for example a divide-by-zero).

Clear the error

1. Fix the cause first. Correct the program (e.g. guard against divide-by-zero), restore the correct PLC ID/password, or repair wiring/supply as the message indicates.
2. Latched special-register problems should be cleared with the module powered off — power down, then back up.
3. For a latch error, flip the Run/Stop switch to STOP, then back to RUN to clear it.
4. General first step for transient faults: cycle the 24 VDC power. But only after reading the error — power-cycling a real program or hardware fault just re-raises it.

Step-by-step

1. Online in ISPSoft → PLC → Information — read the exact error message.
2. Fix the named cause (program, memory, ID/password, latched register, or wiring/supply).
3. Latched register / latch error: power off/on, or toggle Run/Stop STOP→RUN.
4. Re-download a corrected program if the fault is a damaged/incorrect program.
5. Verify the ERROR LED is off and PLC Information shows no fault.

Verify

After the fix, confirm the ERROR LED is off and ISPSoft's PLC Information reports no error. If the same message returns, the cause is still present — re-check wiring, supply, and the program logic (a divide-by-zero or bad math is a common repeat offender).