Using Auto Regulator in a Solar Array

I'm asking this question in Car Audio, because I thought that car audio people would be the most capable of answering my question which regards DC electronics and automotive parts. Forgive me, I didn't know who else to ask. So here it is:

I'm interested in using a scrap automobile regulator in a solar panel array. Here's my concern and question:
Auto regulators are usually connected to the alternator which suggests they are regulating AC voltage. Are they taking AC as input and producing AC output or do they have an inverter built in? Additionally, I can't find information explaining the difference between AC and DC voltage regulators. Can I use an AC regulator in a DC sys tem and expect the same results?

I will have to look it up, but I believe a cars regulator takes the AC from the alternator and converts it to DC. The regulation part is where it determines how much curreent (power) the alternator is putting out to supply the cars electrrical needs.

Paul, I believe you are correct. I was beginning to suspect this based on my continued research. It sounds like car regulators have a rectifier built-in (AC to DC). And I think the rectifier happens after the voltage regulator.

I really can't seem to find any scrap parts anywhere that would be useable. It looks like the best option is to buy a solar charge controller voltage regulator on ebay. Unless someone can point me to a supplier for cheap DC-DC (step-down) regulators.