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Hi folks, I have a small problem and hope someone here can help me!

I am new to the AIU world and am wiring up the AIU to power sidings threw 10amp relays. For some reason it is not working, I have a 12v power supply that I am using to power the AIU and the relays, but when I hit the button on the remote I can hear the AIU relays switching but nothing is happening at the Relay board. Here are a few photos to show what I have.


The lights on the relay board doesnt come on and the power out does not change! Any help would be great! STAN I know your out there! LOL


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Mike how about a wiring diagram. Things just do not look right to me. I assume the AIU is supposed to trigger a relay. Where do the black and red jumpers go/do? 

I guess the white jumpers on the AIU provide power to the AUI internal switch and the green wires distribute power to the relay.  The relays need to be connected to common in order to throw a solenoid (or what ever is being used these days) and you do not show what happens to the relay side of the business. I do not have any relay boards so maybe I am just blowing smoke?   

Jo Jeff, o will upload a wire diagram tomorrow,  the red and black wires go to a 12v power supply, you are correct about the white wires and green wires. With the help of @Mark Boyce o did an ohm test and have continuity when spose to. I followed his wire set up, but something is messed up on my end cause it works great on Mark's  layout

Mike, if I recall correctly, I had a similar problem when I first connected mine.  At first I used two different wall warts, one for the AIU contacts and the other for the relay board.  Bill had used the same wall wart for everything.  When I went to one wall wart it worked.  I have no idea why.  Now after working on yours yesterday, I have no idea why it won’t work.  As you said, you disconnected everything, and start over with just one connection from AIU to relay board.  I’m going to take a nap 😴

Use one wall wart. Two didn’t work for us.

Be sure that the relays are configured properly.

We used orange and white wires to connect the wall wart. In a couple of places, I decided to use black wire instead of orange… that was dumb. Note how the wall wart is connected to the relays. Yours are not done in this manner. I would probably try changing this before disconnecting everything.

We always tested the first relay to be sure that things worked. Our first AIU was defective. Thank goodness we caught it.

If this makes no sense, call me and we can walk thru it. I think you have my number. If not, let me know and I will send a PM.

This process is one of the delights of this hobby 🙄😲🤨

Wall wart used black and white. Be sure the AIU is working.


The next three used orange and white.



This and the next hilite the relay jumpers



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That is the only difference that I see assuming that your relays are the same.

Before Christmas I rewired the yards and switched the wiring around. It didn’t work. I went back to what we had always done and no problems. The wall wart was the problem.

Try changing it and, if it doesn’t work, lets get on the phone and go thru it. Did you check the AIU with something simple to be sure it is working?

That’s a good question, Rich.  When I was planning my wiring, I was told the early AIUs had 10 amp relays, but later ones had 4 amp relays.  I have 2 new ones and 2 used ones, so I went with a setup like Bill Webb went with for the reason Mike related.  Yes, it was tempting to not go with the extra wiring, but 4 amps was a little close for comfort with more than one engine on a track.

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