how to figure out resistor needed

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=112190
Printed Date: May 15, 2025 at 9:54 PM

Topic: how to figure out resistor needed

Posted By: iteetwo
Subject: how to figure out resistor needed
Date Posted: March 07, 2009 at 8:21 PM

could somebody tell me the proper way to find out what resistor you need to activate the door lock if you dont have a tech sheet.thanks

Replies:

Posted By: i am an idiot
Date Posted: March 07, 2009 at 9:40 PM

Tell us what kind of a vehicle.

Posted By: iteetwo
Date Posted: March 07, 2009 at 9:45 PM

its a 2006 caravan

Posted By: i am an idiot
Date Posted: March 07, 2009 at 10:04 PM

USE A 2K OHM RESISTOR TO ARM AND LOCK. DOUBLE PULSE A 5.2K OHM RESISTOR TO DISARM AND UNLOCK. MAY NEED TO USE RELAYS. SEE VEHICLE DOCUMENTS FOR REAR HATCH AUTOMATION.

I am sure that it is a typo, having the 1 wire system with 2 different pins of the same connector on the BCM.

Door Lock Circuit	1 WIRE SYSTEM
Power Unlock	VIOLET/GREEN	(-)	PIN 11 ON C3 CONN. AT BCM
PowerLock	VIOLET/GREEN	(-)	PIN 21 ON C3 CONN. AT BCM

Posted By: iteetwo
Date Posted: March 07, 2009 at 10:11 PM

i think you missed my point.i want to know how to figure this out without having a tech sheet to tell me which to use.thank you

Posted By: i am an idiot
Date Posted: March 07, 2009 at 10:26 PM

I thought that was what you wanted but when I asked what kind of vehicle? I was waiting for the answer you just gave. Since you told me what kind of vehicle you were asking about, I did the research for you. How are you going to find the wire without the tech sheet? If you can find the wire without the sheet, you will have to get an assortment of resistors and try them untill you get it to lock or unlock.

Posted By: iteetwo
Date Posted: March 07, 2009 at 10:36 PM

so how does somebody figure it out besides looking at a car manual or tech sheet.thats what i want to know

Posted By: ajstetler
Date Posted: March 07, 2009 at 11:57 PM

Okay look, you were given bad advice about determining resistor values for locks. You don't just try a bunch until it works, that's ridiculous. This is what you have to do. If you are starting from scratch assuming you know nothing about the vehicle, go to the source. You need door locks, so go to the switch. After gaining access to the lock switch, you will need a DMM to figure out resistance, if any. In your case, first test the suspect wire for voltage. The voltage will read less than 12 volts at rest on lock and unlock, and go to ground when pressing lock or unlock. Now, figuring out the resistance- cut the lock/unlock wire in half. Test the switch side of the cut wire and set your meter to ohms. Place one lead to a good ground source and the other lead to cut side of lock wire. Press lock, that will give you resistance #1, press unlock, that will give you resistance #2. Faster than the "process of elimination" test. I hope that makes sense, that's an awful lot to type and to have it all make sense!

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Big Al

Posted By: chriswallace187
Date Posted: March 08, 2009 at 4:27 AM

Or you could just unplug the switch and measure the resistance between the terminals in both positions.

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C Renner's Auto Electronix
My service is cheap, quick, and good - pick any two

Posted By: howie ll
Date Posted: March 08, 2009 at 4:49 AM

Damn you Chris, beating me again that's how I found out the first time I did a Voyager!

Posted By: iteetwo
Date Posted: March 08, 2009 at 6:32 AM

thanx for the post ajstetler. i knew you dont just get a bunch of resistors and try them.