ChuckD

I have stripped the interior because it was in such horrible shape. I plan to sell some parts. How do I test them to make sure they work without wiring them back into the harness? Can I ground them and then run current to them straight off the battery? I am talking about rear wiper motor, antenna, analog clocks, etc. I am still reading books on electrical theory for cars, but I guess I haven found one that answers this question. Will the battery only supply what the component draws? Or...will will it supply all the amperage it has on tap and fry them up? Sorry for what is surely a stupid question.

Mrmerlin

yes you can test from the battery,
just make sure the test leads dont touch as you can weld them together,

danglerb

Battery supplies voltage, current depends on the resistance of the device.

I have a Power Probe III which has a switch for applying power to test devices and uses an internal fuse, but if you are careful I think any garden variety probe will work.

Be sure about what you touch to what, shorts make heat fast.

Don't test near the battery, fumes are explosive.

17prospective buyer

Think of DC just like water flow, water flows based on potential. Also i have to disagree on the fumes thing, yes some conventional batteries produce hydrogen as a product of the chemistry, but i'm pretty sure they only produce a large amount when taking a charge or a huge draw is on them. Don't think a tiny motor is going to produce any gas to be worried about.

LT Texan

I used little bitty wires when hot wiring the WUR for testing.

They gave the ultimate sacrifice when my fat fingers shorted the connection.

Mrmerlin

FWIW the lead acid battery will always have fumes and more of them when being charged.
Any errant sparks can ignite the fumes and thus a battery explosion happens

chrisjbell

Use smaller wires so if you short 'em they don't weld together - they vaporize like a fuse blowing. Hurts a lot when holding the wires with bare hands - just don't short them. :-)

Battery chargers work well for testing stuff like that, too. Safer - breakers built in.

GlenL

That's a good idea.

When you're doing something like this you'll be impressed with the power of the battery. Just today I was testing some fans with a battery and when the leads touch the contacts there's a spark and the leads get a little spot-weld to the contacts.

When working on some stuff I'll use a test light in series. That's a 12V light bulb with wires soldered to it. If I accidentally connect it to a short the light comes on. It reduces the power a lot so fans, lights and actuators seem sluggish. Usually work, though, so you know the thing works. Or it doesn't and the light doesn't come on which says the test target is "open" and likely dead.

Have fun!

danglerb

Test light as mentioned above is like $5 at HF, just make sure its the simple old school type unsafe for use with electronics (safe ones are WAY too low of current).

Modern battery chargers won't turn on unless they see voltage from a battery.