AIU conundrum

My dcs system  comprises a Z 4000, 1 TIU and 3 AIUs. The relays in the AIUs power Z1000 switch motors. The switch motors are powered independently by a ZW. All AIU ports contain 1/4 watt resistors to provide constant lighting to the Z1000s. Last week the switches in the first AIU stopped working although I could here the relays opening and closing within the AIU. Also the switches powered by the second and third AIU continued to operate normally with the handheld. Strangely, those turnouts wired for non-derailing continue to function properly. None of the turnouts from AIU 1 light up , but all in AIUs 2 and 3 do. All wiring,both hot and common, appear intact and tight. Do AIUs have fuses? Do they wear out? Can anyone shed some light on this problem and perhaps a plan to get AIU 1 back up and running. Thanks for any help.

 

 

Original Post

If practical, can you re-route the modular phone cables so that rather than TIU -> AIU1 -> AIU2 -> AIU3, you have, say, TIU -> AIU2 -> AIU1 -> AIU3.  The idea is to see if the problem follows AIU1 or if the problem remains with the first AIU in the daisy-chain from the TIU.  Obviously the switch names on the remote menu will be incorrect during the experiment.

The AIU SW relay contacts go directly to the screw-terminals.  So if you're hearing the "click" I'd say it's fair to assume the closure is being made.  If you have a meter, you should be able to probe the screw-terminal contacts and see the meter "jump" for the 1/2 second (and it's indeed exactly 1/2 sec) when you trigger an SW port.

If you used the Z-Stuff controllers as well as the AIU to control switches, you wouldn't need the added resistors.

If  you hear the relays opening & closing, your problem is not in the DCS system, but the wiring.  ?#1 Are you getting power (I assume you're feeding common, with a hot wire serving each switch motor) to the center terminal of all 10 AIU relays?

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