continuity tester ?

On 1/12/2010 5:35 PM mark krawczuk spake thus:

How about a 12-volt light and a 12-volt buzzer wired in parallel? Can it get any simpler than that?

If you want voltage indication, wire a DMM in parallel with all that.

--
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Let's NOT use a 12 volt light and a parallel buzzer on any electronic engine/transmission/chassis/drivetrain control modules.

Some of the electronics uses the CAN bus (a communications system designed for vehicle control). The oscilloscope pictures here

indicate that the CAN signals are in the range of 5 volts. 12 volts via a test lamp may cause damage to the electronics in one or more control units.

If the vehicle is pre-1990, there's less to be damaged. Pre-1970 vehicles are almost bulletproof...

A DMM in the hands of someone who won't try to check volts with the meter set for amps or ohms is usually safe.

If the vehicle is 1996 or later, you can learn more about it's status much nore safely wih an OBDII reader such as this one (under $30US including shipping)

plus a PC (preferably a laptop) with a USB port, and some OBDII display software (TouchScan is $30US, EasyOBDII is free, wOBD is free

- all of them display status and error codes and can clear the error codes - TouchScan has configurable dashboard displays and multiple "trip memories").

John

On 1/12/2010 9:10 PM snipped-for-privacy@jecarter.us spake thus:

OK, granted, but when I read "continuity tester" I assumed that what was wanted was something to check ordinary (i.e., 12-volt powered, non-electronic) devices in an automobile. Which may or may not be the case with the OP. Obviously, more sophisticated test equipment will be required around any electronics.

--
You were wrong, and I'm man enough to admit it.

- a Usenet "apology"

While not a continuity checker, Harbor Freight has DMMs on sale for a whopping $1.99...you can't even buy a light bulb for that amount.....and it does so much more.

With modern vehicles, you need absolutely minimum current or risk damaging sensors and other components. A light continuity tester is a strict no-no...

Just a DMM, with a beeper, will work just fine, their current is very low and won't damage things.

Just avoid lamps and buzzers that are powered directly through the test loop.

I bought a couple of the Harbor Freght DMM's for non-critical use (AC line voltage & 12 volt battery checks) and was plasantly surprised to find that the two I have track closely with the Fluke 77 DMM I have for electronics work.

John

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Check out the PowerProbeIII at

This is the tool the pros use. It's a bit on the pricey side for the occassional user, but has all the features the OP requested, and more.

--
David
dgminala at mediacombb dot net

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