My Actuator Only Moves in One Direction — What's Wrong?
An actuator that extends but won't retract (or vice versa) points to a specific set of electrical or mechanical causes. Work through this checklist to isolate the problem in minutes.
Most Common Causes
| Cause | Symptom Detail | Likelihood |
|---|---|---|
| Faulty DPDT switch / one half failed | Works extend, dead retract (or vice versa) | Very common |
| Limit switch tripped and stuck | Stops at one end and won't reverse | Common |
| Control box output failure (one channel) | One direction button gives no response | Moderate |
| Broken wire in one polarity path | Works one way, motor silent the other | Moderate |
| Mechanical jam at end of stroke | Motor hums but rod won't reverse | Less common |
Diagnostic Steps
1. Bypass the switch
Temporarily connect the actuator wires directly to the power supply in reverse polarity. If the actuator moves in the "dead" direction, the actuator itself is fine — the switch or control box is the problem.
2. Test the switch with a multimeter
Set multimeter to continuity mode. Test both halves of the DPDT switch in both toggle positions. A healthy switch should show continuity in each position. If one position is open, the switch is faulty — replace it.
3. Check limit switch state
If the actuator stopped at the end of stroke and won't reverse, verify the internal limit switch hasn't mechanically stuck open. Drive the actuator manually (by hand if possible on smaller units) a few mm away from the end, then try again.
4. Inspect the wiring
Check the wire colour that would carry current in the non-working direction. Look for breaks, corroded connectors, or loose terminals. A broken wire in the motor negative path will prevent one direction only.
5. Test the control box output
Use a multimeter on the control box output terminals. In the non-working direction, the voltage should switch polarity relative to the working direction. If the voltage stays at 0 V in the dead direction, the control box has a failed output stage.