Kerry; I think that you could probably make a 12V solenoid work without a problem on a six volt system. A solenoid is basically an electromagnet with an iron or steel slug riding inside of it, as long as it has enough current going through it to produce a field it will work. The voltage rating is the maximum safe level at which the solenoid can operate without burning out, it doesn't mean that it won't work with less. Converting six volts D.C to a higher voltage is a tricky business. The D.C has to be converted into a pulsating voltage first and then to be run through a transformer to step it up, this is accomplished with an inverter circuit. The trouble is that most inverter circuits are designed to step up a voltage a great deal more then from six to twelve volts, usually 6 or 12 volts dc to 110 volts A.C. A circuit could definitely be made for this purpose but the time and cost would not make it worthwhile when the solenoid would likely work without it. If it doesn't it would be easier to add another six volt battery in series with the car batteries and the window switches to make up for it. I am quite surprised that there are no 6.3V solenoids available as it was a common voltage in electronics, even with solid state for a long time. Best Regards Arran Foster 1954 Imperial Newport Needing A left Side Taillight bezel and Other Trim Parts