Test for disarm
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=70683
Printed Date: July 15, 2025 at 11:29 PM
Topic: Test for disarm
Posted By: Alpine Guy
Subject: Test for disarm
Date Posted: January 13, 2006 at 2:00 PM
This may seem like a scary question, but i have never learned it before. How do you test a disarm wire on a veh? Usually i have just been winging it and hoping for the best, no problems so far, but thats the only single thing on a remote starter install that i can admit i have no idea how to test for. Hitting the DL, or the factory fob while probing the wire with a DMM never shows anything, what do i need to do? ------------- 2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Replies:
Posted By: dualsport
Date Posted: January 13, 2006 at 2:45 PM
Maybe the pulse is too short for the DMM to pick up, since the display update time on a DMM is so slow-
Maybe you could try putting one of these together to see if it'd pick it up with the yellow LED-
logic probe
Posted By: mike swanson
Date Posted: January 13, 2006 at 2:48 PM
heres what I do... I hook my test light to power then probe the wire. with the test light hanging on the wire take the key and unlock the driver door with the key in the key hole. the test light will light up showing ground. Or set off the alarm and then grond the wire. This will shut the factory alarm off.
Posted By: dualsport
Date Posted: January 13, 2006 at 3:05 PM
Just have to be extra careful using test lights if you're not reasonably sure you have the right line, since they can inject power, which some electronic components might not like. Some DMMs have a pulse display that can show up short term signal changes; if you're in the market for one anyway, you can look for one that has that capability. Or a handheld scope, if overkill is good.
Posted By: mike swanson
Date Posted: January 13, 2006 at 3:28 PM
Just have to be extra careful using test lights if you're not reasonably sure you have the right line, since they can inject power, which some electronic components might not like.
YES test the wire 1st to be sure!!!!!!!!!!!
Posted By: Alpine Guy
Date Posted: January 13, 2006 at 10:42 PM
Humm, so if the car can be disarmed from the key in the door i can test that way, ,or set off the alarm and ground out the wire. Sounds good to me. However such as a 2002 Explorer, i find 3 wire in the kick panel matching the described disarm wire and they all test (+), what do you do there? ------------- 2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Posted By: Ravendarat
Date Posted: January 14, 2006 at 12:13 AM
test by using the key in the lock tumbler, almost all vehicles can have their alarms disarmed by using the key tumbler. Now heres a trick though, for some reason some vehicles disarm wires will only test when unlocking the PASSANGER DOOR. So you might have to turn the key in the passanger door instead of the drivers door. If you are gonna try setting off the alarm then grounding the wire, than make sure that you use a fuse holder with something like a 1-3 amp fuse so that if you are wrong you have a chance to save the system.
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double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer
Posted By: Alpine Guy
Date Posted: January 14, 2006 at 10:15 PM
Humm, very good info, im liking this, thanks. As for the fused test connection, i definately have been using that for a little while now already, i have a 1 amp fuse in it, works great, if it pops then i know its not the right wire.
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2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Posted By: dea,can
Date Posted: January 15, 2006 at 1:25 AM
*****DO NOT USE A REGULAR TEST LIGHT ON THIS VEHICLE.YOU MUST USE A LOGIC PROBE OR MULTI-METER, OR SEVERE DAMAGE WILL OCCUR TO THE VEHICLE'S COMPUTER.
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dragon
Posted By: Alpine Guy
Date Posted: January 15, 2006 at 10:12 AM
Yup, i have a logic probe and "had" a DMM till last week, someone decided they wanted it more than me  , i would never use a test light. Only use the ground thingy when needed to test a circuit rathar then just grounding it out unfused. ------------- 2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Posted By: dualsport
Date Posted: January 15, 2006 at 11:38 AM
Just be careful even with the fused test line method, because using a 1A fuse might still be trouble to the electronic components, even though it'll protect the wiring. If it's a logic signal you're trying to drive rather than a relay, you could try putting something like a 1k resistor in line, which would limit the current to a safer level while being able to drive a high impedance input.
If the circuit you're testing is driving a relay coil, it'd need more current, so you could either use a low current fuse or smaller resistance in line to safeguard against a misprobe.
I'd always try to start with a DMM voltage probe to first see if it makes sense; e.g. if it's reading ground already, it obviously can't be a ground triggered input. Checking the open circuit voltage to see if it's 5V or 12V also could give you some indication if you have the right wire.
If you're fairly sure you have the correct wire, you can skip the preliminary checks and try actuating it, but better to be safe if there's any doubt, since it could get expensive otherwise.
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