How to test to see sensors are working?

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=16645
Printed Date: November 04, 2025 at 5:35 AM

Topic: How to test to see sensors are working?

Posted By: phamine
Subject: How to test to see sensors are working?
Date Posted: July 24, 2003 at 8:00 AM

How do you know if a sensor is working or not?

Replies:

Posted By: xetmes
Date Posted: July 24, 2003 at 10:25 AM

Maybe a little more info on what sensors?....?

Posted By: phamine
Date Posted: July 24, 2003 at 4:11 PM

specifically a shock and glass. I see a light on the sensor lighting up when it detects shock or sound - but it doesnt set off my alarm when they do sense it. Sensitvity is on high for both sensors

Posted By: xetmes
Date Posted: July 24, 2003 at 5:43 PM

Hmmm.. if they are lighting up they should be triggering the alarm as far as i know. Did you isolate them with diodes? Are you sure all the diodes are facing the correct directions?

Posted By: phamine
Date Posted: July 25, 2003 at 6:56 AM

posted_image

The band side of the diode is facing towards the sensor. There is my wiring. Upper right is my ground, middle is my multiplex negative output, and lower left is power(grey wire coming from Backup battery). The red wires coming from the wire loom are just the wires I used to extend the harness from the alarm brain.

That's how I connected the wires from the sensors.

The sensors do light up, but I've notice that when they are triggered, the voltage drop on the negative output wire only drops from 12v to 8v.

I triggered the hood pin switch and notice the voltage drop on the same wire was from 12v to 0v. I'm not positive if the voltage drop matters for the sensors. What voltage drop is needed for the alarm brain to trigger the alarm?

Posted By: phamine
Date Posted: July 25, 2003 at 6:57 AM

posted_image

Here is how I wired the shock sensor - connected the green wire to the blue one.

Posted By: draasch
Date Posted: July 25, 2003 at 7:00 AM

most alarms use a neg trigger for sensors do you have three wires for each sensor??
red 12v hot
blk ground
blue trigger wire (if this wire see a ground it will trigger the alarm)

and maybe a green ( this wire would be for a pre-warn chirp) such as a double stage shock.

-------------
Good Luck
David
Ace Security
813-376-9778
Tampa
Donate to the 12volt

Posted By: phamine
Date Posted: July 25, 2003 at 9:04 AM

Yes, 3 wires you've stated.

The thing is that the sensors do not ground the alarm(both shock and glass). There is only a voltage drop of of 8v from 12v on the neg trigger wire from the alarm.