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How Do I Wire a Three-Wire (Limit-Switch) Actuator?

Many PA actuators ship with three wires instead of two. The third wire connects to the internal limit-switch circuit, enabling automatic stop at full extension and full retraction without external relays.

What the Three Wires Do

Standard PA actuators use two wires for motor power. Models like the PA-14 and PA-04 with internal limit switches add a third wire that routes through the limit-switch contacts in series with the motor circuit.

Wire Colour Function Notes
Red Motor + (extend direction) Positive terminal when extending
Black Motor – (retract direction) Positive terminal when retracting
White / Yellow Limit-switch common Routes power through internal switches; open-circuits at end of travel
  

💡Check your datasheet: Wire colours can vary by model. Always verify against the product datasheet on the PA Resources page.

How to Wire It

1. Connect power supply

Connect your 12 V or 24 V DC supply positive rail to the input of your DPDT switch or control box. Connect the negative rail to both the actuator's black wire and the switch common negative.
 

2. Wire extend direction

From the switch's extend output: connect positive to the actuator red wire and return negative through the white/yellow limit wire back to the switch negative rail.
 

3. Wire retract direction

From the switch's retract output: connect positive to the actuator black wire and return through the white/yellow limit wire back to the switch negative rail. Polarity on the motor wires is reversed relative to step 2 — this is correct and what makes the motor reverse.
 

4. Test end-stop behaviour

Drive the actuator to full extension. The motor should stop automatically when the internal limit switch opens. Repeat for full retraction. If it does not stop, recheck that the white/yellow wire is in series, not bypassed.

 

Do not bypass the limit wireConnecting the actuator as a two-wire unit (ignoring the third wire) removes automatic end-stop protection and can stall the motor against the mechanical stops, shortening motor life.

Using a Control Box Instead

PA control boxes such as the PA-20 and PA-22 handle limit-switch wiring internally through their 4-pin connector. If your actuator came with a 4-pin connector, plug it directly into the control box — no manual limit-wire routing required.