I spent some time today figuring out how to use a couple of the supporting components for my build. These include the power steering pump, DC-DC converter, and coolant heater.
I used a Chevy Spark charger (same as the Volt's) as a high voltage power supply and powered up the components. The DC-DC is from a Ford Focus EV. It powers up its output immediately upon application of high voltage. This is extremely convenient for me, though I imagine it could cause trouble with precharge in other conversions. This isn't a concern for me though. The low voltage wiring is 3 wires. Two wires are a differential data pair and the third seems to be floating. I thought it might be a disable line but it doesn't seem to respond to having 12V put on it, though I was using a 10k resistor and it appeared to clamp to a bit over 5V. I wasn't game to try a lower value resistor, so I just left it be, happy that it works anyway.
The coolant heater is also from the Focus EV. Super simple PWM input to drive that. The charger wasn't up to the task of driving it (which is good, since I clearly didn't have any coolant in it!). It did seem to react to the input signal I fed it, so I'll play with it more once it's in the car. This is used for the cabin heater and battery heating, when required during charging.
The power steering pump is from an Astra. I had to buy another one since the one I installed in the car wouldn't power up. I tested this one on its own and it spins up happily, so I'll swap them tomorrow.