The easy part about using a regular 9V battery is that you don't have to worry about safe operation.
You can dead short the battery and nothing is going to blow up.
When you short the battery, it can't deliver the amps so the voltage takes a huge dump and there is no power transfer.
You can test for voltage on your tongue and easily bring it to the scrapyard to test stuff.
If the component works with only 9V and milliamps then it should work with 12-14V.
You can make your own tester with leads using an old 9V battery.
You remove the connector at the top of the old battery and use it to clip in some wires.
I touched the wires together a bunch of times and couldn't get it to spark.
You can dead short the battery and nothing is going to blow up.
When you short the battery, it can't deliver the amps so the voltage takes a huge dump and there is no power transfer.
You can test for voltage on your tongue and easily bring it to the scrapyard to test stuff.
If the component works with only 9V and milliamps then it should work with 12-14V.
You can make your own tester with leads using an old 9V battery.
You remove the connector at the top of the old battery and use it to clip in some wires.
I touched the wires together a bunch of times and couldn't get it to spark.