My husband's horn keeps going off during the day and night. What causes it and how to repair.

Hello, it is very likely that there is a concern with one of the door switches which shows that a door is being opened when it actually is staying closed. If the vehicle thinks a door is being opened, it will set the horn off as an anti-theft measure. I would recommend some testing be performed related to the door switches on all opening panels. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops

I had this happen with a car before and it was connected to the alarm, or actually it was the alarm. They set it too sensitive, so it kept going off everytime a slight breeze went by. If it's that then you just need to take it back to the place that installed it or most mechanics can do it - they just need to make minor adjustment so it's not so sensitive.