12V test light

[bwringer]

I think that would be fairly easy to build with a project box and a few parts.
A variable potentiameter would do the trick, current would vary with voltage and resistance setting.
If you wanted to be really fancy it could include a shunt and an ammeter as well.

I like a speaker and a light for remote monitoring. Some of my test equipment now has bluetooth/wireless monitoring which is nice, but adds an extra set of batteries to maintain.

Thanks -- and I agree that this seems like it wouldn't be hard to build. So I can't quite figure out why it hasn't been built and slapped on Amazon already. "Replace your random assortment of scavenged light bulbs" seems like a sure-fire sell to all the world's mechanics with blistered fingers.

If you confine the scope to vehicle wiring, then that makes it much simpler. Heck, you could even build in some sort of protection or automation to protect or serve the doofs who might try to poke the probes into a wall socket.

 

[RPH]

Resistance decade box in series with leads. Start at highest resistance value and go down. Get exactly what you want in indication.

 

[theoldwizard1]

Resistance decade box in series with leads. Start at highest resistance value and go down. Get exactly what you want in indication.

Yes, but bulky ! No visual or audio indicator.

 

[rockettauto]

You want a sealed beam headlight, around 4.5 amps. My main voltage drop bulb is a 2amp unit.

For those who don't understand why you need a load - you load a circuit then check for voltage drop on the power and the ground. An LED test lamp or meter can show voltage, but not ability to flow current. I can have a rotten starter wire that has a single strand of good copper. It'll show B+ all day long, but won't illuminate a 4.5 amp lamp. This is also why resistance testing is no good for testing ability of a wire to supply a load. That rotten cable will show B+ at the starter, but that rotten cable will never supply a 500amp inrush current.

Yes. I had a good example today. Not nearly as extreme but same scenario nonetheless.

97 f150 stich in 4wd. New encoder motor before I got it, switch tests to absolutely perfect resistance levels. 12v seen at the motor leads when activated.

Testing supply to the transfer case relay control module showed good voltage there, and of course at output since it was seen at the motor.

Standard test lamp would light up at the supply wire to the tcrcm but not on the outputs.

Jumpered the motor at the tcrcm connector and plink, it shifts out.

Bad relay in the " module" ( really just two relays on a board in a housing) would switch voltage appropriately but not pass even the little bit of current necessary to light the bulb let alone drive the encoder motor.

 

[AJHD]

Anyone who is a frequent viewer of SMA will see Eric use handmade test lights (and factory made) in many of his video. Just used one the other day diagnosing a bad blower motor resistor.

Jarhead Diagnostics also makes and sells them on his website. But I'm not paying the asking price, even if they look professional.

 

[2ndGearRubber]

Resistance decade box in series with leads. Start at highest resistance value and go down. Get exactly what you want in indication.

Those things don't always like big current flowing through them, the cheap ones anyways. I have a cheapo resistance box and there is a noticeable odor from it when using it as a load.

Anyone who is a frequent viewer of SMA will see Eric use handmade test lights (and factory made) in many of his video. Just used one the other day diagnosing a bad blower motor resistor.

Jarhead Diagnostics also makes and sells them on his website. But I'm not paying the asking price, even if they look professional.

Jarhead stuff does look really nice. I like the guards for using normal modern headlamp bulbs, instead of needing a sealed beam headlamp which is bulky and tends to roll off whatever I have it sitting on.

 

[ZiggyMacD]

Short It Out And Look For Smoke!

Got a kick out of this one, old school tricks to the rescue!