Horn relay

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=88749
Printed Date: May 12, 2025 at 8:16 AM

Topic: Horn relay

Posted By: aknavy
Subject: Horn relay
Date Posted: January 11, 2007 at 12:25 AM

I'm sure this has been addressed, but I can't find wiring instructions that work for me. I've got a 97 suburban, and I'm using an alarm with a + siren out. Horn requires a negative input to set it off. What is the proper way to wire the relay to make it work? Thanks for the help.

Replies:

Posted By: Twelvoltz
Date Posted: January 11, 2007 at 6:55 AM

If the system offers a "Horn Honk Output" then it is usable. But if it only has a siren output you would need to incorporate a flasher into the circuit as a siren output would work fine for locking and unlocking but would give a constant honk if the alarm is set off (picture holding the horn button down for the full alarm duration). Anyway to wire the relay to convert from a positive to a negative here is one way:

Pin 86: Ground
Pin 85: Positive Siren Output from Alarm
Pin 30: Ground
Pin 87: Vehicle negative horn wire

Here is where you would find the diagrams on this site.

Posted By: aknavy
Date Posted: January 11, 2007 at 12:34 PM

The alarm has a switchable + siren/horn output. I measured it and it transitions from 12 - 0 while alarming, but I was having problems getting the relay to energize while it was alternating. The only time I got it to energize, the output stayed hi. I'll try what you posted. Thanks.

Posted By: aknavy
Date Posted: January 12, 2007 at 4:58 PM

Found I had a bad relay - replaced it and works perfectly.