Relay To Isolate Wire From Lock/Unlock Switch?

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=148299
Printed Date: May 02, 2025 at 4:34 AM

Topic: Relay To Isolate Wire From Lock/Unlock Switch?

Posted By: mmh1
Subject: Relay To Isolate Wire From Lock/Unlock Switch?
Date Posted: March 13, 2025 at 5:24 PM

Hi,

Could someone explain what the notes highlighted in the box means..."Relay to isolate wire from lock/unlock switch".
posted_image

I'm just learning so would appreciate the help.

Thanks,
M

Replies:

Posted By: lee.lopez
Date Posted: March 13, 2025 at 6:18 PM

What is the year/make/model vehicle? Here's an example of a relay isolating diagram, but probably not the one you need:

https://www.the12volt.com/relays/relaydiagram3.html

Posted By: kreg357
Date Posted: March 13, 2025 at 6:55 PM

The relay is used to isolate the vehicles lock switch from the aftermarket devices (-) Lock output signal.

Here is a diagram for the added relay.

posted_image

Under normal operation the vehicles Lock signal passes thru the relay, Pin 87A to Pin 30. With a aftermarket Lock signal output, the relay is energized. This opens the normal vehicle Pink Lock wire path through the relay and puts a (-) on the vehicles Lock wire going to the Fuse Box connector only.

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Soldering is fun!

Posted By: mmh1
Date Posted: March 14, 2025 at 4:58 AM

It's a Smart Fortwo 2008 UK model auto.

Posted By: mmh1
Date Posted: March 14, 2025 at 5:01 AM

Thanks Kreg and Lee for taking the time with the diagrams and explanations; really helped my understanding.:)

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