Tell us about yourself!
Since you say that this inverter will output 230 volts, can it be used to power a household through the fuse panel in the house?
Firstly, there is hardly ever an easily accessible 12 volt power source under the steering wheel of any vehicle. Most use a clockspring mechanism for accessories that are steering wheel mounted. Fooling with this will most likely result in loss of the accessories. Secondly, to leave the wiring running down the column and not leaving enough slack to let the steering wheel turn fully from lock to lock could be fatal. Thirdly, fooling with anything to do with the airbag system without knowledge or training will most likely result in severe injury. Please add safety warnings about what you are instructing to prevent serious injury or worse!
For freezing temps, put a similar copper tubing grid inside the tank. Plumb the two grids together and fill the system with RV antifreeze, used when storing your RV in winter. Now fill the storage tank with water and plumb this heated water into the house system. In central Canada, we continue to use the standard hot water heater in the house and feed it from the storage tank so that the main heater only has to run a short time, if at all. This way, with proper shutoff vales and drains, we can drain the solar heater system, leaving the antifreeze in the solar part with no damage when the outside temp gores well below freezing. Easy-peasy!!
Actually, Titebond III will work even better! It is totally waterproof.
I can't see exactly how the Dremel is secured to the base you have made. Could you please advise us?