How do you bench test electric parts

[irl]

Can someone explain how to bench test lights and other electric parts away from the car. I am working on a wiring harness in the basement while it is 25 degrees in MD and I want to also bench test some parts. I get the positive side of things but I know everything is grounded in the car, how is this accomplished on the bench if necessary.

[timmy2]

So, I'm assuming you have a 12 volt charger capable of 15 amps of current, or a similar DC source for testing with.
The Positive lead from your source is for the positive side of the devce you are testing.
The Negative lead from your source is for the negative side of the device.
The negative is also what you refer to as ground on our cars.(Negative side of battery goes to chassis ground)
Good luck, be careful, and find a way to put an in line fuse between the source and device you are testing.

[dshepp806]

As Timmy noted, you'll need a good DC power Supply if you're looking to "actively" test the "device". (pass current). Your DC connections will be as it would for a battery.

Best!

Doyle

[Tremelune]

Pull that battery, or get ahold of a battery and use that. Keep it topped up with a battery tender.

Another fun trick is to use an old computer PSU. A lot of them will do 15A+ DC on a single 12V rail easily. You usually have to jump a cable or two (google around), but it's a good method to get figured out. It will pay dividends when you need to test other stuff in the future. They can be found for $0.

[Walt Fricke]

Easy source of 12VDC power - your car's battery. Pull it out and put it on your bench. After you use it for this or that, you can use a charger to refill it. One of the small, inexpensive ones which can be mounted on the battery itself would be good for this also, as they can sense when it is charged and quit charging, so you can just leave them connected.

[irl]

Yes I bought a smaller 12V battery to use. I didnt realize negative was ground. Thanks so much for the comments. I also bought a unit called a power probe III that will help.

[fastfredracing]

The power probe is an awesome tool for bench testing low amperage devices on the bench. You will learn to love this tool. Keep it away from computers, and modules.

[hydrocrust]

Or get inexpensive 12 volt supply from eBay or amazon or Northern. They are $30-40, handy for troubleshooting (just tested and replaced one of my horns).

[Walt Fricke]

Wow - I don't think there has been a positive ground car since maybe the '60s. Something British, most likely.

The speedometers of '77 911s had the instrument in the case insulated from the case ground so they could be used with positive or negative ground cars, but I have always wondered why, as I don't think any Porsche was ever positive ground.

[tocobill]

What they said. Ground is Neg. I used to use a 12v jump box as it was always plugged in so you didnt have to use a tender to keep it changed.

[irl]

Walt,
Wasnt thinking the car was a positive ground system, i just didnt realize the negative terminal was considered to be grounding. Thanks for everyones help.

[timmy2]

irl.
As an electrician for 30+ years and training many, many apprentices. I knew this was the conceptual challenge you had. That is why I put it in bold for you.
Yep the whole car body is negative/ground.
Not to worry. I have many conceptual challenges, lately my 17 yr old son has been the main source!

[Porboynz]

Originally Posted by timmy2

irl.
As an electrician for 30+ years and training many, many apprentices. I knew this was the conceptual challenge you had. That is why I put it in bold for you.
Yep the whole car body is negative/ground.
Not to worry. I have many conceptual challenges, lately my 17 yr old son has been the main source!

My 17 year old is providing a conceptual challenge right now, at least 12 volt electrics can be explained whether they be negative earth or positive.