Can a test light do damage?
 

I've used the same old style test light for years. Never had a problem. So, go to the 2 minutes mark on this short video. Truth or fiction? Is it worth tossing my old light and buying one that uses LED's?

https://www.youtube.com/watch?v=bmCGgDtCAYA&ab_channel=JoeCanDoIt

(I watched the whole video)

With the number of computers in a modern car... Anything that can potentially mitigate an accident is worth investing in.
And LED test lights are not expensive.

"Having said all that" I still use a traditional one for both of my cars but they're ancient. If it ever breaks or I lose it I'll buy a newer LED light for sure.

I had treouble wrapping my head around the bit on the bulb test light drawing too much current % causing harm while the LED light doesn't...hope someone really into electrictronics can weigh in...

LEDs draw a FRACTION of the current that an incandescent bulb draws. Not only that, but they are DIODES. Current limiting devices.

That's why your LED light bulb in your ceiling light is so cheap to run, the watts are very small compared to the equivalent brightness incandescent.

Thanks...

I seem to remember being told there was a chance of frying the CD (capacitive / discharge) box on the early 911 ignition system if probed with a test light.

Home Depot used to have a display of an incandescent bulb next to an LED bulb running nonstop with meters measuring electricity usage on each, showing how much savings there is with LED.

I heard a story once: Apparently a test light set off an air bag. Probably like most things you'd hear pre-WWW - BS. However now it's even worse! What probably happened: The idiot was snooping around messing with something he should've left alone. He just happened to have a test light in his hand when it went off.

What I have seen first hand: An airbag deploying during a race on a closed circuit for no apparent reason! Maybe he hit a large bump?

Test light schmest light . If you really want to mess up some electronics, you need a power probe . One of the most useful tools I own, but I have fried a module before

Many of the wires coming out of the ECU are meant to carry a small handful of volts rather than a full 12V. I know this because if you get into testing a single component you may find that the particular wire to one of the contacts only carrys say, four volts.

I don't know how a 12V bulb could destroy the ECU if you tested it with a traditional light on that line. It may be what he's talking about?

It's unlikely, not impossible. 5V signals should be probed with a high impedance meter, scope, noid light, or logic probe. But it is pretty unlikely that a 12V bulb will fry an output.

If you're using an incandescent probe, why are you probing 5V lines? Know what you're doing or accept the consequences.

Like Fred said, don't inject 12V without being sure where it's going.

no wires "carry volts"

volts is measure of potential. wires carry amps.

Well, whatever...being a tool junkie anyway, and figuring it's cheap enough, I ordered this.

https://www.amazon.com/Upgraded-Automotive-Voltmeter-Portable-Stainless/dp/B0B4VP117Y/ref=sr_1_4_sspa?crid=2W8L3S52KK1Q6&keywords=Innova +continuity+tester&qid=1694540019&sprefix=innova+c ontinuity+tester%2Caps%2C178&sr=8-4-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

Can't hurt to use the LED version. I never thought about it so thanks for the info.

But I've never used a test light on anything except lighting circuits. Maybe a motor circuit like a window regulator. Hopefully those are all still 12v.

You're both wrong. Wires carry angry pixies.

A test may say "test for 4-5 volts." I put the MM on it and read the voltage.

I could test for amps separately.

Somehow the volts are at the end of the wire, says the accountant. Where did they come from? Not arguing. Just asking.

volts are a measure of difference, think one side of the circuit is a hill, thats the high volts. the low lands are all low or no voltage. amps are a measure of flow. ie, how much is moving from high on the hill, to low on the hill.

Thank you. That makes sense to this layman. I did some googling and read the electrons wiggle. Nothing flows. I have read that umpteen times. One forgets if not used consistently.

I am glad I have the little bit of knowhow I do.

charge moves, not electrons. charge is what amps measure the flow of.

The tester I ordered arrived today. Works well. Lights up red for positive polarity, green for negative, and the voltage display matches with my cheap multimeter. I'm thinking it might make some things easier & quicker than using the multimeter, like checking fuses...