So you know your line hot, load and neutral wires?
If so, can you take pictures of both switches before the modification and label the wires you identified? Unless you don’t want to do this. I just want to start fresh and find out your current wiring. We both could learn something from this.
Absolutely!
My goal from this is to figure out a way to implement it and then share the information in some sort of write-up that makes it dead simple to understand given the correct wiring (obviously).
Also, @Snakedog116 here are the diagrams for the Monoprice On/Off In-Wall Relay (single relay)
I enhanced the numbers on the 2 switch diagram because they were a bit hard to read.
Ideally, the control a light with 2 switches would be ideal… but who knows if it’s possible with my wiring or not. But given that I have constant power to the switch box… I’d think this could work. I just don’t know what the numbers mean next to the switches on these diagrams.
Annotated photo at one of my switch boxes.
It is to be assumed that on the other end is just a 3-wire romex with ground coming into the box and some other switches and hot bundle / neutral as well.
Actually, just found this diagram online…
I think this is my wiring setup for this particular switch… 
Colors and all.
And here is my altered diagram showing MY INTERPRETATION of the monoprice 11989 single relay controlled with 2-switches diagram based on my wiring in my switches:
It should be noted, however, that I believe this is one of the configurations I tried last night and it did not work… but I may be mistaken
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If you are using the single relay, you are right, they changed the colours for some bizarre reason. The single relay manual has a diagram right in the manual. Just use that!
You said you want to put together instructions to make it dead simple, unfortunately every electrician will wire this a different way, and some just use whatever colour of wire they have etc. It’s not always clean and simple, you kind of need to draw out what you have, and then look at the manual.
The drawing you just posted is the same as the other diagram you posted which I thought you said isn’t what you have:
If this is what you have, then it’s just like a normal switch. Leave the switch without constant power alone, and install the relay where the constant power is, just like a normal switch.
What you are doing is:
- Plug the hot and neutral wires of the relay to the hot and neutral bundle so it has constant power.
Then disconnect the black wire that is coming from the light into the switch. (in your photo you labeled it as black (common?) wire running to load). - It used to go to the switch, but now put it onto the load wire of the monoprice relay (red on both the dual and single relay).
- Then the switch end of the relay goes to where that black wire black (common?) wire running to load used to be connected (on the switch itself). For the dual relay it’ll be blue, for the single relay it’ll be green… don’t ask why, but that’s what the instructions say.
(Note, for a single relay it looks like the blue wire goes to the constant live wire, same as the black one. For a dual relay you’ll have 2 wires left over, a single relay you’ll have just the one)
Yeah, unless I’m mistaken I believe this photo I took last night was how I set it up last night.
Which I believe is the same as my diagram… so I’m not sure why the switches didn’t work but the relay would.
Again, I could be recalling this incorrectly so I may just have to give it another go but still…
FYI, I’ve now annotated the photo I posted last night with the module ran as I described in my diagram above… which (if I recall correctly) just made it so that the relay could power the light, but the switches had zero impact on the relay or the light.
Also, not noted in the image but the white relay wire is bundled with the neutrals
So the only thing I can think is, if you’re thinking this should be working… is that the switch in the other switch box isn’t wired just right for this relay? That’s really the only thing missing from my photos is evidence that the other switch is wired as my diagram states… but I can’t imagine it is not since it works in general when plugged in as a standard 3-way hmm…
Another thing I just found from the Customer Reviews page on the Monoprice 11989 Single Relay switch…
No, the other switch shouldn’t affect the monoprice relay at all, you didn’t change anything there.
Yea, I’m really not sure about what to do with that silly blue wire. Monoprice’s manual says to put it to the hot wire, but I’m not sure why that would be necessary. That description you found in the reviews is very similar to the manual. Perhaps try leaving both the yellow and blue wires unattached.
If you want to test the relay, you could disconnect the green wire and try to manually plug it into the neutral bundle. That should tell you if there’s an issue with your switches or something else.
How sure are you that you have a single relay instead of the dual one? They look identical, same wires coming out etc.
Well, I’m fairly sure I have the single relay’s…
But here is an image I just made of them side by side.
The one in my photo that was attached to my switches has the yellow and green together like the Single Relay.
Side-note… these little white cases look to be able to open up.
Wondering if I opened one up and painted it with liquid electrical tape if it would save room in my switch boxes… (guessing as long as the chip itself is non-conductive with the liquid tape on it then it should be safe?)
Plus I could figure out the physical differences between the two chips… I’m betting not much is different and those extra wires are fairly pointless…
Another review from that screen talks about the 3-way setup… does this offer any insight?
And another review, this one mentions them having it wired into a 3-way setup and it’s working so obviously I can do it, just gotta figure out exactly how. haha…
Wait, this dudes name is Kris too… coincidence @Snakedog116 ? 
I just ordered a batch of the MP single-relays last Friday with the sale to continue connecting my existing 2-ways to ST.
However, I have a couple 3-ways I would prefer to connect first, so I will be working on this tonight or tomorrow night once they arrive. If you’re still working on the configuration, I’ll pitch in to help.
@tgauchat
What issues?, I have 30 of these, including two dual versions, I don’t have any issues with any of them.
Great to hear! Yep take photos and document your progress and findings.
I’ll do the same.
Wait, this dudes name is Kris too… coincidence @Snakedog116 ?
@joshuairl, nope, that must be a different Kris, but it’s nice to know that other people know how to spell my name right… 
Have you tried to wire the relay in as per your last diagram? I see no reason why this wouldn’t work. Please get back to us once you’ve tried that with the results. The setup is actually fairly straight forward if you have power in the box that sends the signal to the light. If you look at the manual you’ll notice the 1 switch and 2 switch diagrams are basically identical…
In that review he references changing the programming of the relay. Have you programmed the unit yet? It seems like this could be a really simple thing to miss, not sure who thought that the most common use is with an indicator light…
