using dmm’s?
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=21525
Printed Date: July 06, 2025 at 8:08 AM
Topic: using dmm’s?
Posted By: HamiltonAudio
Subject: using dmm’s?
Date Posted: November 15, 2003 at 7:07 PM
guys, we all know that a DMM is a much safer way of probing and testing wires in a vehicle than a test light. But how many installers out there are still using lights? My pal works at a competing shop...we all know and love the "Power Probe" tester, its a wonderful tool...but this guy will very boldly pulse circuits right off of ECM's with this thing... I called powerprobe and they assured me it is not, and never was claimed to be computer safe...to me, he's pretty ballsy using this probe in new vehicles with all the multiplexing and computerization....I tell him that all the time...but he swears there has never been a problem.. how do others feel about it? b
Replies:
Posted By: xetmes
Date Posted: November 15, 2003 at 7:52 PM
i dont understand why they dont have actual computer safe test lights freely avaliable, i could build one with parts lying around with an input impedence of around 200 Megaohms, and draw about 50 nA (50 x 10^(-9)) A or .00000005 Amps, although it would require external power (a battery)
Posted By: NowYaKnow
Date Posted: November 15, 2003 at 11:53 PM
If I am being lazy or in a rush I will use my test light in cars I know just to "double check" myself but a car I'm not familiar with I break out the meter..I've seen even the "computer safe" test lights trip air bag lights and other strange things happen..
Mike
Posted By: HamiltonAudio
Date Posted: November 16, 2003 at 8:43 AM
you're right...I've seen lots of strange things too....good example is a 2003 Avalanche. standard stuff for GM, and when they attempted to start it up with the key, it had gone into passlock lockout...and they hadn't even touched the PL wires yet!!!!! spent 10 mins shorting the battery cables  I feel uneasy about probing in unfamiliar cars with anything but a dmm....those PowerProbes are the handiest things in the world, but they aren't computer safe....wouldn't a computer safe version be neat?? PowerProbe, are you listening??  b
Posted By: italnpimp59
Date Posted: November 16, 2003 at 7:37 PM
yeah really the only thing i use a test light for on a car is to find a blown fuse or to find power and accessory wires when i have to hardwire a head unit. as far as an alarm...nonono....bad idea. i have never had anything bad happen to me from it, but i have heard lots of stories of weird stuff happening when probing with a test light. airbags going off...making the trunk pop open when you probe that wire with test light...i even heard of headlights blowing out! yeah a computer safe test light would be great. installers all over the world would be buying them!!
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Posted By: sroth140
Date Posted: November 16, 2003 at 8:24 PM
a guy at work fried a computer with a test light, $960 to fix.
Posted By: HumbleI
Date Posted: November 16, 2003 at 8:29 PM
What is a dmm??
Posted By: xetmes
Date Posted: November 17, 2003 at 4:59 AM
Digital multimeter
Posted By: HumbleI
Date Posted: November 17, 2003 at 5:53 PM
ahhhh ok lol glad I asked... thank you very much!!
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