An RJ-series electric valve actuator at one plant showed intermittent feedback: the remote "closed" status signal came and went while the "open" status was normal, and the local display was fine. When maintenance shorted pins 17 and 18 of the power plug, the remote-closed status displayed correctly again. This article analyzes the symptom and the isolation method.

Symptom Highlights

• Remote "closed" feedback intermittent; "open" status normal
• Local display normal — the actuator's own status logic is sound
• Shorting pins 17/18 restored the remote-closed indication

Analysis

Pins 17/18 are the remote-closed status contact output (or its pick-up point). Restoring normal display by shorting means the internal status logic is good — the fault lies in the contact itself or the field loop:

• Contact degradation: oxidized output contacts or weakened leaf springs make intermittent connection
• Field loop: loose DCS-side terminals or oxidized cable joints — "comes and goes" feedback is typically a contact defect
• If the short was made at the logic-board side, the board contact/relay is the suspect; if made across the cable ends (bypassing the unit), the unit's output contact is the suspect

Isolation Method

• Sectionalize: measure the contact pair at the terminal strip from the actuator side and the DCS side — unstable on the actuator side = logic board/relay group; stable there but unstable on the DCS side = cable and terminals
• Check the relay group: in the actuator's status query menu, verify the closed-status relay operates consistently with feedback
• Treat contacts: clean oxidized contacts or replace them; replace failed relay-group modules via RagA spares
• Re-tighten the field loop: DCS-side terminals, cable shielding and earthing

Takeaway

• Nine out of ten "intermittent" feedback signals are contact defects: sectional measuring (actuator side vs DCS side) locates them in minutes — far faster than swapping boards
• The shorting test is a powerful tool: normal after shorting = logic and unit are fine, the fault is in contacts or field wiring; still abnormal = logic board
• Feedback defects do not affect valve travel but mislead operations monitoring — fix them promptly to avoid misjudged operations

Related reading: RAGA Electric Actuators: Wiring & H01–H10 Parameter Commissioning