Horn working inconsistently with fob (locking)

[Seal]

I got this car maybe month-month and a half ago and there is an issue where sometimes the horn will sound when using the key fob to lock the car and other times it will not.

While doing some work on my MS3 this weekend I noticed I need to replace the negative battery clamp as doesn't seem to stay tight. I was wondering if that could be an issue. I wanted to know if anyone had a wiring diagram showing how the alarm wires to the horn. I'd like to check to see if there is a lose or intermittent connection.

The horn works fine from the steering wheel so I'm thinking there is something with the alarm to horn wiring. I changed the fob battery and it is a strong 3v so I don't think it is the battery.

 

[Awafrican]

old car battery causes lots of issues, I notice if my fob battery is getting low it doesn't work so well in the cold even before I get the low fob battery alert.

replace that terminal and toss a new fob battery in as a start.

all the wiring diagrams and shop manuals are in the members section accessed via donation ($10/yr) but they are save able you don't need to keep the access once you download them

 

[Easter Bunny]

Horn only sounds when all doors are closed. Tech package may need hood closed too. Could be a door sensor going out

 

[Seal]

old car battery causes lots of issues, I notice if my fob battery is getting low it doesn't work so well in the cold even before I get the low fob battery alert.

replace that terminal and toss a new fob battery in as a start.

all the wiring diagrams and shop manuals are in the members section accessed via donation ($10/yr) but they are save able you don't need to keep the access once you download them

Thanks, I’ll jump on that manual donation option!

I haven’t replaced the terminal yet but was able to bend it to get it to clamp a little harder and the horn beep seems to be working consistently now. I’ll see if it continues to work after the terminal replacement.

EDIT*** Looks like the semi loose negative battery connection was the culprit as I have no had the inconsistent issue since getting the negative terminal snug. I still need to replace the terminal connector as it reaches a point of no longer tightening.