Changed battery on idle 2004 GMC 2500HD, Now Horn Keeps Blowing While in Use

[Kshinn2]

I own a 2004 GMC 2500HD that was purchased in 2005, has been well-loved, and has been used for horse show towing until the last few years (due to work and personal surgeries). All highway miles.

 

This truck does have a very high-octane alarm that was installed after we purchased (not sure why?), That is very sensitive.

 

Fast forward to now. The truck hasn't been used in 6 months and the battery was just replaced, but now truck runs... With the HORN running intermittently...?!

 

Does anyone have a reason or solution for this?

 

Also, I'm looking to sell... As my new husband has a truck as well. 

 

Thank you (in advance) for your help!

 

[Jsdirt]

Those aftermarket alarm systems are notorious for being low quality garbage (in addition to poor installations). In the long run, they end up causing more problems than they solve. 9 times out of 10, whenever a vehicle gets towed to me for a no crank, or no start, it's an aftermarket alarm system that's the cause. If it were mine, I'd tear it all out and throw it in the trash.

 

You'd be better served with a home camera system (or even a dash cam that will record upon motion detection), and a toggle switch hidden in the cab that kills spark, fuel, or both.

Edited August 3, 2021 by Jsdirt

[Doug_Scott]

Between the title and the description I find it near impossible to figure out the question. At first I thought he changed his battery while the truck was running, not the smartest thing to do, and damaged the horn relay.  But then after reading the story I thought maybe this was as simple as stale fuel setting off the sensor and all he needed to do was disable the sensor until he was sure the old fuel was burnt off.  Then Jsdirt brings up aftermarket alarm system issues, so who knows now. 

I am near Toronto in Canada, if you want to flog it off cheap, let me know. 

[Kshinn2]

The truck sat for a while and after the battery was changed, the after-market alarm keeps going off while the truck is in use. 

 

Also, sorry about being confusing... I'm a girl, lol

[Jsdirt]

Could try disconnecting, then reconnecting the battery once, or a few times. If that doesn't fix it, the only fix is to toss the system in the trash.

[Kshinn2]

Thank you!! Will try that!

I have zero problem tossing the alarm system at this point...lol