Troubleshooting F0-04DAH-2 Analog Output on CLICK PLC: No Voltage

Problem Overview

A CLICK Series C0-06 (Click 06) PLC is fitted with an F0-04DAH-2 four-channel 0–10 V analog output module in slot 1. Ladder logic uses IBox IB461 in BCD format with K4 channels, writing scaled values to V2000. The internal register V2000 updates correctly (0–65535) as the operator input on V2200 (0–250) is scaled with LDD V2200 → MULD K65535 → DIVD K250 → OUTD V2000, but the module produces no voltage on any output terminal and the channel-active LED never illuminates. The drives that will eventually receive the analog signal are not yet connected, and the only external wiring is the 24 VDC field supply to the module power terminals.

System Configuration

F0-04DAH-2 Module Specifications

The F0-04DAH-2 is a four-channel voltage-output analog module for the CLICK Series. Key ratings that matter for this fault:

Root Cause Analysis

The combination of "valid data at V2000 but no LED, no voltage, even with a meter" almost always reduces to one of four field issues, in order of probability:

1. Module power not actually present on both required inputs. The F0-04DAH-2 has a 24 VDC input for the digital/logic side AND a 24 VDC input that feeds the analog output drivers. Both are required. A single shared 24 V lead that is properly terminated at the power terminals of the CPU base but not at the analog module's separate power input will leave the CPU happily writing to V-memory while the module never energizes its DACs.
2. IBox not executed every scan. IBox instructions are not edge-triggered coil-like operations. They execute as long as they are reached in the scan. If an unconditional contact or a stage skip is in series, or if the IBox is below another IBox that fails, the module never sees a new write and the LED stays dark.
3. PGM→RUN transition not performed after the IBox was added or modified. CLICK analog IBox instructions register their slot/channel configuration on a power-up or PGM-to-RUN transition. An IBox added or edited while in RUN mode will not be honored until the transition occurs. A power cycle alone is not always sufficient if the IBox was edited in PGM mode and never re-saved.
4. Corrupt scratchpad (system-parameter memory). Analog I/O configuration data is stored in the CPU's scratchpad area. Old project data, especially from a different slot map, can leave the slot 1 IBox pointed at a non-existent module. Initializing the scratchpad forces the CPU to re-acquire every expansion slot on the next power-up.

Step-by-Step Troubleshooting Procedure

Execute the following checks in order. Do not skip ahead — items 1 and 2 are the cause in the majority of field cases for this exact symptom.

Step 1 — Verify the IBox is on an unconditional rung at the top of the program

Open the CLICK programming software and confirm:

• IB461 is the first instruction on its rung.
• There is no contact, stage bit, or subroutine gate in series with it.
• No stage programming (SG / ISP) is used that would skip the IBox rung.

If the IBox is gated, remove the contact or move the instruction to its own rung with no preceding logic, then save and transition the CPU to RUN.

Step 2 — Power-cycle AND transition PGM → RUN

With the IBox saved to the project:

1. Place the CPU mode switch in STOP (PGM).
2. Power the system down for at least 10 seconds.
3. Power up. Wait for the CPU to complete its expansion scan (the "EXP" LED behavior settles).
4. Toggle the mode switch to RUN.

Per the CLICK Series User Manual, an IBox added or edited in PGM mode is not executed until the next STOP-to-RUN transition. Editing in RUN mode alone is not enough on CLICK C-Micro firmware.

Step 3 — Initialize the scratchpad

If the module still produces no output, clear the CPU's system memory. The scratchpad holds analog I/O configuration that can be left over from a prior project even when the project file is otherwise correct.

1. In the CLICK programming software, connect to the CPU.
2. Navigate to the system/setup menu and select Initialize Scratchpad (sometimes labeled "Initialize User Memory" or accessed via the CPU menu — the exact menu path varies by CLICK programming software version, but it is under the CPU/setup functions in Do-more Designer or CLICK Programming Software v3.x and later).
3. Confirm. This clears all V-memory and system parameters including the IBox slot map.
4. Re-download the project.
5. Power-cycle, then transition to RUN.

Step 4 — Confirm the 24 VDC power arrangement

With a DMM on the F0-04DAH-2 power input terminals (de-energize first, then re-energize to measure), verify two 24 VDC sources are landed correctly:

Reference: F0-04DAH-2 datasheet wiring diagram. If the module is powered only from the CPU base's internal 24 V and the field 24 V is not landed at the module's power input, the module will not drive its outputs even though the CPU sees V2000 change.

Step 5 — Re-seat the module and inspect the edge connector

1. Power down.
2. Remove the F0-04DAH-2 from slot 1.
3. Inspect the gold fingers on the back of the module for contamination, oxidation, or bent pins.
4. Inspect the slot connector in the base for the same.
5. Re-seat firmly. Power up, transition to RUN.

Step 6 — Force a mid-scale write to one channel

To isolate "module never wakes up" from "module wakes up but data path is wrong":

1. Temporarily change V2200 (or write a constant) so that the IBox sees 125 (50%).
2. The math 125 × 65535 ÷ 250 = 32767 should land 32767 (0x7FFF) at V2000.
3. Place a DMM on channel 1 output (+) and a common terminal (−).
4. Read approximately 5.00 VDC.

If 5 V is present, the module is healthy and the original "no voltage" reading was due to either (a) V2200 being held at 0 or (b) the scaling math being performed on an inactive rung.

Verification Procedure

After the corrective action, perform the following acceptance test before reconnecting any drive:

1. With the module powered, DMM on channel 1 (+) to common (−), mode switch in STOP/PGM — reading should be 0.000 VDC (outputs are de-energized in PGM).
2. Switch to RUN. With V2200 = 0, read 0.000 VDC. With V2200 = 250, read 10.00 VDC ±0.05 V. With V2200 = 125, read 5.00 VDC ±0.05 V.
3. Channel LED for the active output should illuminate continuously in RUN when the channel is enabled in the IBox.
4. Repeat for channels 2, 3, 4 by moving the DMM probes and verifying the IBox channel enable mask in the IBox configuration dialog.
5. Sweep V2200 from 0 to 250 in 25-step increments and confirm output voltage tracks linearly. Any step jump > 50 mV indicates a noisy 24 V supply or a ground loop; address the field wiring.

Troubleshooting Matrix

Common Field Pitfalls

• Confusing the two 24 V feeds. The F0-04DAH-2 has 24 V for the logic/DAC section and 24 V for the analog output drive section. Wiring only one pair is a common first-time error. The module datasheet shows both terminal pairs explicitly.
• IBox edited in RUN mode. On CLICK C-Micro firmware, IBox slot configuration is locked at the PGM→RUN transition. An edit made in RUN does not take effect until the transition occurs.
• Reading commons with an ohmmeter while unpowered. A non-zero reading is normal because the internal common bus is a PCB trace. Check commons only with the module powered and the system in RUN.
• BCD vs. binary format selection. IB461 supports BCD and binary data formats. If the format is wrong for the source data type, the count value written to the module is not what the math suggests. Confirm the format dropdown matches the data type at V2000.
• Channel enable mask. If only one channel is wired and the IBox is configured for 4 channels, the unwired channels will sit at 0 V — this is normal and is not a fault. Leave the IBox at K4 channels and only the enabled channels drive the bus.

Safety Notes

FAQ