How to replace a nearside signal microswitch

Replace the microswitch when a nearside signal switch is inoperative or gives a permanent demand. Replace the full barrel if the fault remains or water ingress is present.

Before you begin

Only competent traffic signal personnel should complete this work. Isolate the equipment, prove it is dead and follow the controller and site safety procedures.

Check for water ingress

Water droplets or white or blue deposits around the microswitch
A microswitch that fails within one year of replacement
A complete switch that fails within one year of street deployment

If any of these signs are present, replace the complete switch assembly. Return removed parts to AGD with the full serial number and site location for investigation.

Replace the microswitch only

Remove the two screws from the halo PCB.
Disconnect the cable loom from the switch terminals.
Carefully release the securing lugs on the sides of the switch body and remove the microswitch.
Fit the new microswitch squarely and confirm that both retaining lugs are fully engaged.
Reconnect the cable loom and refit the halo PCB.
Restore power under the approved procedure and test full switch operation.

Replace the complete switch barrel

Remove the tactile unit and sounder if fitted.
On AGD946 and AGD947 products, remove the green aspect PCB.
Disconnect the switch cable loom and remove the halo PCB.
Using suitable pliers, turn the switch barrel clockwise to loosen it, as specified in TAN31, then remove it by hand.
Install and tighten the replacement barrel using the approved method.
Refit the halo PCB, reconnect the loom, and refit the green aspect PCB where applicable.
Restore power under the approved procedure and test full operation.

Applies to AGD nearside signals including AGD946 and AGD947 variants referenced in TAN31

Source TAN31 issue 2