You have to understand that so called "voltage reducers" are simply resistors. You must diddle them depending on the amperage of the load. The common ones available at the parts joints are designed to drop 12-6 (actually 14-7) AT A CERTAIN AMPERAGE LOAD.
This means that if the wipers draw a lot less than the blower, the blower will run way slower, the wipers way faster.
So "rig" it temporarily, MEASURE the load voltage with a meter, and go from there. The resistors at the parts joints have a chart that shows a combo of 1, 2, 3, 4, etc resistors in series/ parallel arraingments depending on the load amps.
Another way around this problem on a vehicle that is not used so much everyday is either two 6V batteries or a tapped 12V. A good battery shop should be able to supply you with a tapped battery. There's a special relay used to be avail. from stores, but in reality you just need a good heavy relay, or continuous duty solenoid. You operate the coil from the key, and run the loads through the contacts off the 6V tap on the battery. Just another way of doin' it.
The common parts store unit is (example) Standard Motor Products (you've heard of Blue Streak) RU-100. Just about all parts stores sell the same item.
Never try to use these types of drops on your electric guages. Use a "Runtz" regulator instead. Just Google Runtz. They are essentially 5V regulators, and if you Google up the do it yourself Mopar instrument regulator, you can make those, too.
For your coil, buy a 12V coil and matching resistor for any 60's--70's Mopar or Ford.
The 6V starter does not care, and your 6V solenoid will probably be OK
Don't forget to wire it NEGATIVE ground. You'll have to reverse the ammeter if you have one
If you are going to run a generator, be sure to get a regulator which matches the generator AMPERAGE as well as TYPE. Very very important. You will have to POLARIZE (flash) the generator, and pay attention to what TYPE you have because the procedure will vary.
