finding 12 volts

I am a part-time installer for a type of vehicle security.
Sometimes it takes forever to find constant 12 volts - especially newer vehicles.
I tried placing a tone injection across 12 main i.e. across the battery and thought I should be able to pick it up throughout the vehicle. Not really. Probably too much fat wiring etc drags down the signal too much for the inductive pickup.
Just a thought - is there something else one could use here?
Another type of tone injection tool or something like that if u know what I mean?
Thanks

""""Digital"""" Multimeter, Period

digital multimeter is the best way to go especially with all the newer vehicles but sometimes i still use a high dollar SST test light on older vehicles. good luck and hope this helps.

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"I cannot teach anybody anything, I can only make them think."
-Socrates-

You can always get one at ign harness or fusebox.

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Why oh Why didn't i take the blue pill
Darren Power

Guys - yes of course a multimeter is needed. Use it all the time.
But I guess I was wondering if there's a tool to find 12v without having to pierce wires. Or at least something that would let me know that constant 12v is in the area without first having to cut open loom, harnesses etc. and test each wire or the ones that I suspect have 12v anyway. For instance, I have a tool for tracing long runs of computer ethernet cabling. It injects a warbling tone at one end, then with a second piece, an inductive pickup, you just wave it close to the general area, behind wall etc., and it finds the tone and hence the wire location. I was hoping something like that exists. Like I said I tried it on a vehicle but it didn't seem to work. Not sure why. I think capacitors, coils and the like kills the tone signal.
What's this SST tool?
Thanks anyway.

Yeah that would be sick, electricians have that tool they can just hold up to a wire, and it will glow if it is live, without piercing... Someone needs to invent something liek that for 12V DC. Id buy 10.

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99 Blazer LT.   Yellow Top. Big 3. Infinity Kappa Speakers All Around. Jensen CD/DVD flip out. 2 Infinity Kappa Perfect 12DVQs powered by a Alpine PDX600.1 (in one custom box, building a FG box)

SST Test Light is a low resistant test light. it can be used on airbag circuits and/or delicate circuits etc and not damage any ECUs. i use it to do alarms test fuses etc. if you check the Liddell factor then you will see that it is compleletly safe to use on any wire during an installation. good luck and hope this helps.

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"I cannot teach anybody anything, I can only make them think."
-Socrates-

Yeah the only reason why that works for electricians is because its AC. And the sensor (that glows) is magnetic.
DC won't do that for us. I'd still like to think that a tone injection would work.

Don't you guys find that on newer vehicles its getting harder and harder to find constant 12v?
Probably cause there's so many systems, computers etc that any persistant current draw is avoided so to not drain the battery.

TF

The SST probe has a high resistance (like a multimeter) which makes it safe to use, not the other way around.

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My ex once told me I have a perfect face for radio.

You just have to know where to look for it. Its always gonna be in the ignition harness, always at the fuse box. Get a wiring diagram it tells ya the insulation color.

oops, geepherder is right the SST light tester is a high resistance rather than a low resistance. i love this tester and would hate to part with it. good call geepherder my bad.

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"I cannot teach anybody anything, I can only make them think."
-Socrates-