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I have converted the AC system to 24-volt thermostat and relays so I would need to wire in an interim relay to make the 24 to 12-volt jump to the AH unit. Thank you Richard!  I understand what the switches at the microwave panel do and they are working properly as I can turn on the 110v electric (I only have 30amp in the building) and it works fine.
I did test the continuity and cannot find the wire for the life of me…
W1 = heat on the TStat which is a yellow/black wire on the rear TStat and a yellow wire on the front TStat.

Does the yellow (W1 from TStat) go directly to the AquaHot unit or does it go to the SCS Basement unit board first? 
I have been trying to check continuity using a 20’ 18ga wire from the rear AC (and the front AC) down to the Aquahot and also to the AC units but cannot get any tone out of it. 
I know the continuity tester and wire is good because when I touch the ends together I get a tone (I know enough to know how to do this part)… I’m baffled as to where these wires from the TStat end up.  I know the smaller gauge wires got directly to the SCS AC in a bundle that is twisted into the side of the AC unit via a bung of sorts to make the connections and they are working fine to run the AC units. 
The pictures attached are the AH board/labels with the yellow/black for rear heat and yellow/red for front heat…; and the original 12-volt TStat; the new TStat is an Ecobee with two stages for the AC.

Adrian

As Richard said, you need to change out the two aqua hot relays to 24vac coils to make your heat work. Its a fairly simple wire for wire swap. 2 wires go to the coil and 2 wires will be switched to make the aqua hot come on. Remember 85 and 86 on the old 12v bosch relay are the coil so you need to put that on the coil (#1 & #3) on the new 24vac relay. The other two wires are going to go to the #2 and #4 terminals on the 24vac relay, that is a normally open contact.  

Here are the 24vac relays I used in place of the 12v bosch relays that are there now:
https://a.co/d/bFDrxBA

Here is a short video showing changing out the relays on the aqua hot:
https://youtu.be/NT-QlhW4jgU

Hope this helps.