Helpful 12 volt troubleshooting tip
 

If you have anything that runs in a 12 volt car. You can fashion two wires to it from the positive and negative poles of a car battery and it will zing if it works. It will not damage the battery or the electronic part. After all, it runs on 12 volts when you start the car. Be careful with old batteries as they can explode, but otherwise it's a good troubleshooter for any unknown automotive electical circuit. Everything from fuel pumps, to window motors can be tested this way. I've been seeing a lot of questions about things like this.
I used to scare my cat when he would be laying on an old 1.7 liter 914 motor I had. I would hook the still connected terminals to a battery and the engine would turn over and scare the pee out of him. Good times.

Use a little caution when messing with a battery directly.

Only 12v, but it can do hundreds of amps, so it will spark and can cause burns.

Don't make sparks around the battery, explosive gas comes out, always make the last connection to something away from the battery.

A dedicated 12VDC power supply is much safer; car batteries can kick out a lot of amperage........not only that but what if the said car battery is not pushing out 12 volts? You can buy a good & safe 12VDC for around 20 bucks. When I was restoring/rebuilding my car it proved indespensible for testing all of the electronics and power motors of the car. Pics to follow of my testing setup when I return home from work this evening

I like buying tools, so I have;

Power Probe III
LoadPro
Various cheapo light bulb in the handle probes.

First two are monster trouble shooting tools. PP3 has a meter, speaker for tones and audio work, and its main claim to fame switchable breaker protected ground or 12v at the tip. You MUST know which wire etc you are messing with, but lights, motors, etc. instant go/no go testing. Loadpro replaces a standard probe with a fat one with a button, press the button and circuit draws about 50 ma of current, which instantly detects poor or dirty connections.

I agree that making big sparks is not smart. Nor is doing it in a barn with hay under your feet. I'm saying exercise some control, use some brains, and touch the terminals only long enough to see if something whirs. Don't stand directly over the battery while doing it. It's cheaper than the Power Probe III, but it doesn't have all the bells and whistles. It doesn't have the pussy magnet option. ;)

Here is my 120 AC > 1-12 VDC power supply. I bought the unit from Newark electronics. It's only max 6 amps but it works on all motors in the car. I used it for all seat, window & washer motors. I think it was around 20 bucks; I had extra 3-line cord laying around and I made up a bunch of different leads for the different applications; alli clipped leads are shown. I imagine the "pussy factor" option costs hundreds more though :D
http://forums.pelicanparts.com/uploa...1331650641.jpg

You can also use old power supplies in Computers. I've made a couple with some bolts and nuts for the posts. There are write ups all over Google on how to wire it all up. It's a great way to test 12V stuff.

My Radiator fan wants 35 amps, and three times that to start, so I had to go more robust.

Besides, I like tools, it was around $100, or 50 min of a good 928 mechanics time, or half the price of my Snapon ratchet.

Here's a good write up on the Power Supply. Although, it only makes 12 Amps at 12 Volts, it will power most stuff for testing anyways. Except for the Fan as Mike is stating.

How to Convert a Computer ATX Power Supply to a Lab Power Supply