Thank you for your response. It does makes sense what you are saying. I can try and call RSE instead of email which didn't work. They said in my email that there is a way to do it but wanted me to "look it up". May be it's just too complicated to figure it out with the SPOD.
I'm not giving up yet, there has to be a way to do this on the SPOD SE.
Thinking about this some more, I forgot to account for the fact that the steps go up and down. Assuming this transition is not done mechanically, it requires the electric motors to operate in a forward (down) mode and a reverse (up) mode. My background is high speed data communications, not DC motors, but having a motor spin in both directions probably requires a pos 12V feed and a negative 12V feed. Therefore installing a relay in the pos 12V side will be slightly more complicated, especially if you don't have a wiring diagram. You could use a volt meter and figure out which wire is feeding the pos 12 V to the motors and then install a relay in that circuit. You would use the wire coming from the supply side or from the control side of the circuit as your "power source" wire for the relay. The other side of the relay would go to the motor. Then use the Spod pos and neg wires to control the relay. (If you are unfamiliar with how to wire up a relay, there are simple diagrams that you can google.)
If this were me, here is how I would attack this issue, assuming you won't get any help from RSE.
1. Use a volt meter to figure out what voltage that RSE supplied on/off switch is using for the control side. (Keep in mind if it is an illuminated switch, it will have a 12V feed for the LED light for illuminating the switch in the dark. Don't confuse that voltage with the actual control circuit voltage.) If it is using a pos 12v as the control circuit, then you could simply rewire that circuit into the Spod and eliminate the RSE supplied switch. That would almost be too easy, and thus probably not likely. I am betting they are using a pos 5V for that circuit.
2. If you cannot eliminate that RSE supplied switch, then you have to take control of the motors directly, downstream of the RSE controls. The only real thing that I can think of to worry about is that "reversing if the step detects an object blocking deployment" functionality. I would take a long 2x4 and get a feel for how much force is required to reverse the step during operation. Then install a relay controlled by the Spod and "measure" the force again to ensure that the reversing functionality is still operating as it should. If it still does (and it really should) you will be in business.
Keep in mind that if you retain the RSE switch, both that switch and the Spod switch have to be in the "on" position for the steps to deploy. If either is in the off position, the steps won't deploy. You can either leave the RSE installed and just leave it on all the time or you can hot wire around it and remove it. Personal choice.
At the very least, a wiring diagram will go a long way to simplifying your work. Will RSE hand over a wiring diagram? I would think so, but maybe not. They may view that as proprietary. After all, they did pay someone to design the electronics for them. They may not want that out in the open.
Getting RSE to tell you how to do this is even more remote. Like I said, they most likely contracted with someone to design this for them. They may not even understand exactly how it works themselves. They would probably need to go back to the EE who designed it and ask him or her how to do it. That will cost them money as the EE doesn't do shit for free. So now you are asking RSE to spend money to figure out how to get their system to integrate with an Spod. And they may get one or two requests a year for how to do this. If they don't see a market for this, I doubt they will pursue it. Ideally, it would take a completely different wiring harness so that a consumer could easily tie it into an Spod. That would really take some investment by RSE to make happen. Again, unless they see a market for it, doubtful they would do it. (I actually met the owner of RSE on a trail in Moab a few years ago. Super nice guy!)
I think you are pretty much on your own on this one. It is somewhat ironic that I am in the middle of a similar, albeit much less complicated, situation. I am trying to control a device that is not really meant to be controlled by an Spod. My issue has more to do with the 30A limitation of the Spod though. So just yesterday I bit the bullet and ordered a 40A relay to control it.
If you do decide to pursue the relay option, you can estimate the current draw of the motors by looking at the wiring. If it is 12 AWG wire, its probably a 20A or 25A draw. If its 10 AWG it is probably a 30A to 40A draw. Maybe 45A tops. Make sure you match the wire size and use a relay sized to the wire. I would fuse it just to be safe. And start with a smaller fuse to see how much current it is drawing. Fuses are cheap.
Hope that helps...................(probably not what you hoping for.) I think RSE (or Spod) may have told you to google the instructions thinking there has to be someone out there who has done this already and posted their results on a forum. Unfortunately, you may have to be that someone.